Arguing over what they accomplished in the past (e.g. defeated flesh-murder-monsters or got taken down by a couple bland dolts with hilariously exaggerated popped collars) is a complete waste of time. The true answer to literally every "Who would win in a fight" involving fictional characters is "Whoever the author chooses." I could write a one sentence story about a mouse who defeated Zeus that had no special traits whatsoever, just random chance, and it'd be silly to use that as a basis for arguing that it had favorable odds against Odin. If you take past fights into consideration then all you're left with is a popularity contest, where the people debating are just taking it in turn to hype up the achievements of one of them and belittle the other.
If you want my vote for the popularity contest, I'd have to say the Daedalus edges out the Thermobaric Tank in awesomeness factor, and I still wonder where the people behind Blackwatch found the legions of heartless puppy-kicking starfishs to recruit into their operation, so yeah, STAG again.