I kinda prefer a 20ga #6 for doves (Win 1300 or a Charles Daly o/u). I've used 12 a lot for doves, but after switching to the 20, I get fewer birds that're busted up too bad.

As for shells, I've had good performance for the price with Wolf high brass dove & quail loads. Win high brass heavy game work well, but I can feel the hit in my wallet too.