My initial suggestion was Manila. I really like the stuff that came with Hard Target and think it'd be great to take the Missions setting to someplace completely different culturally, someplace that hasn't really been paid much attention to until recently.
As that's not on the list though, I voted for the Tir. I've always been enamoured with it, partially because I was born and raised in the Portland Area and partially because I like the politics and intrigue nature of it. Also, it has a distinct cultural tone that I find interesting.
Second place goes to LA, I think. I just think it'd be super interesting to see how that area played out. It's a setting I'm not familiar with at all.
I'd be down with the UK and Miami, but they're getting a lot closer to the meh side of things.
I actively don't want either Aztlan or Neo Japan. I feel like Aztlan would have way too much of the cartoonish villainy of the Blood Magic stuff which really doesn't feel like it fits the setting as much as everything else (personal opinion and all that).
For Neo Japan, I'll admit this one is partially prejeduce of characters and players I was introduced to the game with. It was High School (3ed), I knew some people who were far too into anime and "Japan" (not the real place, but the idea of it), and that translated to a really annoying set of tropes that burned me out on the whole thing. Then there's the whole problem with how anti-weapon and such they are, and I think it'd turn Shadowrunning into more of a hassle.
Locations like Atlanta and DC are just boring to me. I'm not a fan of Walking Dead, which I think is based around Atlanta? That's the only reason I can find that it'd be a place people want to run in. Haven't found anything interesting in-game about it. And DC is just... eh. Just strikes me as boring.