Matt- the difference in sizes is not great, but one would be hard pressed to put more than 4 3 blades in a medium quiver. I can put four big Jim broadheads and one thumper in a large, but placement is everything. Now putting 5 terminators in there is not a problem.
You can also put 5 two blades in a medium without a problem and probably 4 two blades in a small.
Just a little heads up for choosing the right size quiver. They are also all quite light so that shouldn't be a major concern.
thanks,bigjim