The difference between weight and size from a 5-6 really isn't that much.

The #5's are 8 ft/lbs of energy per pellet and the #6's are 6 ft/lbs per pellet. However you get more pellets with the #6's, almost 1 and a half times more per OZ.

I would go with whatever load gives you the most even pattern. I don't bother with counting how many pellets I get in a specific area. I just shoot to see what load gives me the most consistant pattern at the distances I want to hunt. I look for a real even spread with no wholes in the pattern. Turkeys are tough, but it only takes a few pellets in the head to take one out.

Paul