I don't know who I should save on Virmire anymore

It's Sophie's choice all over again!

I save Ashley in my playthroughs. Between her and Kaidan, I just felt that her post-Virmire story was better than his. And on the flip side, I found Kaidan's legacy if dead better than hers. I also always have him with the bomb because it makes sense since he has tech knowledge, and Ashley with the Salarians since she is a soldier. And since I always have Kirrahe and his men survive, I always go rescue him so that makes sense which means Ashley while Kaidan defends the bomb with his life.

Having done both I find Kaidan's promotion more believable in ME3 than Ashley's. After working with biotic kids he seems to have gained their respect and a role for himself as a teacher.
He may not be a hardened vet like Ash, but I find it more convincing for him to be a Spectre and called on by the council than her.

Of couse it's not always about the best choice, in my canon I'll lose Tali in the SM even tho she's Shep's bff. That'll devastate her and give her tonnes of motivation in ME3.
Saving the one your Shep hates then loathing them, or learning to work with them, is a great story too.

Both of them are qualified for each assignment. Ashley is a Gunnery Chief who and she should be technically qualified to arm a nuclear bomb as Kaidan. (Remember the guy who drilled the soldiers about physics at Citadel, he's a Gunnery Chief too.) However, Ashley have no history or experience handling military operations with non-humans. Sending her with the Salarian, when she herself is inexperienced that she make casual remark about how she couldn't differentiate aliens and animals, is a PR disaster. I prefer having her defending the bomb because she have a deep grudge against the Geth for massacring her entire unit and this doesn't change in ME3. It drew a parallel to the moment when you met her and she was swarmed by Geth and it fits for her last moments. If I save Kaidan at the bomb site, I'll only hear her death from the comm instead of watching her being badass killing swarms of geth alone.

For me, Ashley's death represented all the deaths in the trilogy : All the soldiers who sacrificed themselves against the Geth, against the Collectors, against Cerberus, against the Reapers. She have the potential to do more and to be more but so was the rest of the faceless deaths. Her sacrifice haunted both Shepard and Kaidan and both of them tried harder to do what is right for everyone they care about and they try to not to take their sacrifices for granted. The way Ashley-alive occupy in the trilogy was her survival is a gift because she is special for the player to save her. In the end, she fall back into the shadows and everything that happened to her are skimmed lightly and there's greater emphasis on her emotional trauma and fragility, especially when romanced. She survived everything and it ate her up and rather than embracing the fact that she should live and fight for the future which people had died for, she wallow up with repressed guilt over the things that happened years before and not for the things that happen in the present.

Whereas for Kaidan in the trilogy, he lost Jenkins on Eden Prime and from Chakwas herself, Kaidan and Jenkins are friends. Then he and Shepard met with Ashley and in turn subsequently they lose her as well. Ashley only feel sad for Jenkins only once in ME1 whereas Kaidan still grief even in ME3. It was something Shepard and Kaidan shared together and it colored their history with a lot of unspoken depth that no ME2 recruit/loyalty mission could replicate. Kaidan was a teenage freak who could kill people with his mind and he got implanted with a faulty tech that give him constant migraine and everyone accuse him for being too whiny when he simply talk briefly about it. And if romanced, he spent years thinking his girlfriend died horribly (thank you, Liara!) and he got blamed again for being angry at her for joining up with terrorists instead of coming home to him. And months later, he watched his home being destroyed by the reapers and choose to save her instead despite the fact that he was abandoning his parents and his friends in the process. After he found out his father died and suddenly he found himself pointing a gun to someone he loves. He's just a guy who wanted to be normal and yet the universe f*cked his life endlessly and he handled himself well and didn't fall apart. I find this as admirable and tell a lot about his character's inner strength and so does my Shepard who loves him.

But I'm not conflicted about Virmire because I don't feel the new writer for Ashley understand her as Kaidan's new writer did for him. She didn't need additional layer of glossy makeup or a skimpy Alliance wetsuit to compete with other potential LIs. She didn't need to have her sister's husband conveniently killed off for a scene to make me feel sympathetic about her situation with her sister who I never met or care. She didn't need to make excuses about why she trust Udina over me and make excuses that he was indoctrinated by Cerberus and she fell for it. She screwed up, own up to it. She didn't need officer training and speedtrack promotion from Operations Chief to Lt Cmdr to validate her Spectre status. She could've replace James Vega as Shepard's lieutenant from the beginning and have James Vega retaining his Lieutenant Commander rank and filling the Spectre spot. She didn't need to be a drunken mess on the floor of my warship and Shepard shouldn't treat it as cute and funny. I should be able to sit down with her and talk about what's bothering her. No matter how much I tried, I couldn't feel any depth for her when I could do so when if she's dead. She's just a damsel who you save over and over since the first game. Nothing more. Which is disappointing since I love Ashley as well.

I don't think Ashley sacrifices herself in ME1 "just to redeem her grandfather."  If she is assigned to the bomb, she sacrifices herself to ensure the mission is completed.  If she is assigned to Kirrahe's team, she sacrifices herself to ensure Kirrahe and as many of his men as possible get out alive (which Kirrahe can live regardless if the player does the things that help the team on his/her way to the breeding facility).

As for making the choice... it's really something that depends on how you want to develop your Shepard (which is about more than just deciding who he/she likes)... For example, if you're playing a MaleShep, locking into a romance with Ashley who is then forced into allowing her to sacrifice herself on Virmire can utterly change how he views the war (in your head canon since it is an emotional area that the developers never really wrote into the game).  Then, say, have him lose his ME2 romance on the Suicide Mission.  In ME3, he can then start a fresh romance with Liara, Kaidan or Steve (or, technically, Allers as well).  In particular, Shepard can, perhaps, feel a much deeper emotional connection to Steve (who has also lost an LI to the war).  With Liara, it can be about discovering that she is the one who has stood by him through thick and thin even though he rejected her in ME1.  With Kaidan, it can be about discovering love after getting beyond a falling out between two best friends.

Really, neither squad mate makes the most sense to arm the bomb.  Tali is the person on the ship who would be most familiar with alien ship design... and the bomb is being jerry-rigged from the drive system from Salarian's ship.  Also, since arming the nuke isn't a combat role (i.e. the bomb being taken directly from the Normandy just a few feet to it's position AFTER the way was cleared by Shepard's squad), Engineer Adams would also be a logical choice to arm it.

I tend to save Kaidan despite being a big Ashley fan. Better she die on Virmire than turn into the parody of herself that is Ashley in ME3. Kaidan's ME3 version is pretty good but Ashley's is horrendous.
Last time I saved her I ended up shooting her during the coup as a mercy. With her dying breath she told me I'd burn in hell and I thought 'that's my girl!'.

Yes, that's makes even more sense than what I suggested.  It really should have been a trade... one Normandy squad member on Kirrahe's team to help coordinate comms in exchange for a Salarian to go on board the Normandy to arm the bomb.

For me: Kaidan

He is a Sentinel which is far more valuable to me than Ashley, as I don't need soldier types -- and James is a better fit for me if I do, anyway.

I like Kaidan's character and story far better than Ashley. Kaidan's story and growth feels satisfying, both as a player and for his character. He gets crap for being a bit of a square, but I've never thought he was "boring." And his being kind of a dork is endearing to me.

I'm not fussed about the whole "Who does what job" for Virmire. Since I often like to use Kaidan for that mission anyway that means Ashley goes with the salarians and I just save Kaidan at the bomb. I rather like the scene of rescuing the bomb-goer too.

Also, he's my space boyfriend. 

I have Ashley alive with one Shep, but I don't really want to play that one because Kaidan isn't there. I don't hate Ashley, I just don't have any real attachment to her and felt she was a big disappointment in 3.

Considering Ashley is my favorite Mass Effect character,? I never have a problem picking.

Why not do two save files, with Ashley alive in one, and Kaidan alive in the other?
To be honest, I really like Ashley and used to save her everytime. But after saving Kaidan in my last play-through and playing through ME:3 with him, I find him to be much more interesting.....even as non-love interest, since I only play stright Males.

Heh, now I'm not even sure if I should go back to the bomb or continue towards the AA tower! I usually go back to the bomb, but now I wonder if that really makes sense? I mean, if Shepard and the crew die, then no one would be around to warn people about the Reapers. No one would look for the Conduit. No one would stop Saren. So shouldn't the Normandy's survival be a greater priority?