Welllll wait a minute now... While these are "low brass" loads they are by no means "weak or slow"! They are advertised at 1290fps, that's faster than most 3" & 3.5" HEAVY turkey loads! Look also at pellet count, in an ounce of #6s there are typically around 225 pellets (+/- 10). Power & penetration aside, to get that many pellets in a #5 load you'd have to move up to nearly 1.38oz. In #4 loads you'd have to go all the way up to 1.75oz. NOBODY would say those 2 loads aren't enough pellets (& mojo) to knock a tom off his rocker!
If a turkey is hit in the head & neck with more than half a dozen #6s it's LIGHTS OUT for him & it doesn't matter if those 6 pellets started out with 1oz of his buddies or 2+oz, DEAD IS DEAD!
Now sure, adding more pellets "should make" for surer hits at further distances but if the OP realizes he AINT toting a 50+yd load & keeps his shots inside a safe range (as determined by his patterning results) then there is no reason to think a Tom is going to laugh & run away after getting a snoot full of 6s inside of 40yds regardless of whether they were from a 2.5oz 10ga or a .5oz .410!
This argument is kin to saying a 150grn bullet from a 300mag is fine but 150grn bullets from a 30/30 AINT! It's all about perspective & knowing ones limitations... As the man said, "A mans GOT to know his limitations!"