In fact there are evidence that bigger queens are best : several studies show that larger queens have a bigger spermatheca and then store more sperm and can mated with MORE different drones than smaller queens. Other studies showed that colonies headed with queens mated with a higher variety of drones had more genetic diversity within its population, grew stronger and overwintered better than colonies headed with queens that mated with fewer drones.. so you can see that the looking for a well developped and heavy queen is not bad. If you look carefully in the colonies that are headed by naturaly reared queens (swarmng queen cells) you could probably see that they usually are much bigger than most of the commercially reared queens available on the market..