If I'm wrong with the timeline correct me, but Loghain would have been a Warden for 20 years after Origins and would likely be facing a trip to the Deep Roads soon. The pragmatic choice from that is that Hawke could do more good since he'd have much more time than Loghain, and I say that as a Loghain fan.
Loghain has been a Warden for about 12 years by Inquisition. He has a good 45-50 years of battle and command experience, fights exactly as well as a much younger warrior in Hawke, is a famous tactician and has connections, knowledge and authority within the Grey Wardens and some pull among Ferelden royalty if Anora is queen.
Hawke is a nobody who had a few years of fame for killing the Arishok and who has only a few disconnected friends, of whom Loghain and Varric are the only ones relevant to the Inquisition's struggle, not even associated with the mages or templars anymore whom you've already dealt with at that point. At least, that's if s/he supports the mage rebellion in DAII. Might have more to offer as Viscount.
In my playthrough the pragmatic option has clearly been to save Loghain over Hawke and try to utilize his talents and connections for as long as he lasts, even if only for the Corypheus crisis.
I didn't said that.
I think is well know by now that Loghain is one of those characters with whom i don't have any problem with and i never liked Alistair nor i like to kill people that could have been saved,but save Loghain to have him in DAI would be a form of ultra metagaming for the warden.
In DAI he is better than the warden because he exist while the warden is just a bunch of letters but i think that is better to make him die for Ferelden and not for Orlais.
"It is better to make him die for Ferelden than Orlais" is metagaming. Deciding that you want Loghain to survive this playthough or that is indeed metagaming. The trick is to come up with an honest-to-god roleplay that you find cool and interesting and which facilitates the story you want to play without breaking character. For me, my depressed Dalish Warden without a future worth looking forward to and my ruthless Inquisitor who would take Loghain's usefulness over Varric's sentimental attachment to Hawke, and certainly Hawke's rumored status as a potential rival for the Inquisitor's own position, any day are what is going to save Loghain this time around. That's not metagaming.
I don't think anyone plays Origins with the idea of Loghain in the sequels as one of the Warden's own motivations. That would be ridiculous.
Loghain's way too easy between Hawke.. for me at least. If I am going to keep him alive, he's got a Redemptive Path written all over him. If he doesn't die in DAO, then it's obscene if he doesn't die in DAI. lol And even he would agree with me. He knows he screwed up.
Of course, I never play Hawke as an outright villain anyways. Maybe then I could kill them.. like if they were slavers or something like that. Otherwise, Hawke doesn't do anything to deserve it.. and their life already sucks as it is.
He can redeem himself when I'm done with him if it means so much. I don't give a used fig for how his story could end with a little extra symmetry. He's strong, intelligent and resourceful, that makes him useful and worth keeping around which is more important than his personal glory or Hawke "not deserving" to die. If Loghain was the last person in Thedas to bite it, fighting and kicking and screaming, then I'd be fine with that and feel better that at least they did all they could with the best they had.