Just my opinion, but I'd opt for the smaller one. Number one, I learned to fly at an uncontrolled field, and I don't have anything remotely akin to "mic-fright." Secondly, security at larger controlled fields tends to be tense. During the time that I worked as ramper (at the same airport), the FBO patrons and I engaged in all kinds of airport mischief such as hanging out on top of the hanger with a scanner and binoculars, watching takeoffs sitting on the edge of the runway, bumming rides in supercubs, recieving numerous bizjet tours, all manner of taxiway and intersection takeoffs, and (horrors) walking around the ramp freely. None of this would have been possible at a larger, controlled airport, and I feel like it is important for a grassroots education in aviation. [LONG LIVE GA!!!] And last of all, you can learn all the big airport skills later (and you will during your private training - it's part of the curriculum). By training at a less busy field, you maximize your primary training time. You have more time in the air. But that's just my take.
Jack @ AUS