FWIW, I think the high dollar "game specific" loads are more of a marketing ploy than anything else.
If a cheaper shell patterns as well as the high dollar shell at the same distances that you're testing them at, then I see no reason to shell out more money for the game specific (i.e. turkey) loads.
As for small shot vs. larger shot, you really can't take the choke out of the mix either. Depending on what kind of gun you're shooting and what choke you're throwing shot through, #7's or a mix with #7's could pattern better than a straight #4-5 etc.
It's a pretty subjective topic, but I believe most people could kill turkeys within 40 yards with most any 12ga shell out there, assuming a well-placed shot and a decent pattern.