I lived in a fairly large city when first getting sober, and when researching it found SMART and AA as the only groups in the city. There were only a couple of SMART meetings a week, but lots of a AA meetings, so I knew I'd always be able to get to a meeting of I wanted to. That was my reason for trying AA first. Luckily for me, it was a good fit (Well, some of my the meetings are anyway, not every single one - there are a couple that I don't find helpful). Now I have moved to a neighbouring city where we only have one meeting each week, and I also travel to the next town for meetings, and sometimes go to the ones in my old city if I'm visiting at the weekend or in the holidays. I always know that there's a meeting I can access on holiday as well. So for me, the sheer number of AA meetings to choose from make a difference to me.
As far as which one to choose to try first. I'd go with, what's the next one you can get to. The only way to know is give it a try. You won't have to say anything at yiur first meeting if you don't want to. My first meeting found me in a room with about a dozen males, mostly retired or enemployed. I had little in common with any of them on the surface, but when they started talking I could listen for the similarities rather than the differences, and there sure were a LOT of similarities once alcohol was discussed!