When I first started playing I flew the LA because of my family's Russian ancestry. After about a month of that I got tired of the horrible ballistics of those cannons and went looking for something that shot straight, ended up with the P-47. I think I chose it because it was the American ride I was least familiar with historically (other than the P39 which I was also very unfamiliar with, but wasn't in the game yet) and I wanted to learn more about it. Also the 8 .50s doubled how far away I could hit moving targets compared to the LA.
I flew the Jug exclusively until some time last month, when I decided I needed to learn more about other planes. I decided to fly the F4U starting this month because it was supposed to be a challenging ride and it could launch off carriers. Also I remembered the F4U from the Battlehawks 1942 computer game manual... that manual was a veritable history book on the pacific theater of WW2, including a great chapter about how incredibly lucky we (the US) were to have our carriers survive the early half of the war. Ironically, the F4U wasn't even flyable in that game, but it was featured in the manual a lot. So I wanted to fly the Corsair first in Aces High.
That's where I am right now, but the P-38 will be my ride next tour.
Oh, some linkage: http://en.wikipedia.org/wiki/Battlehawks_1942