The biggest difference I see in the different divisions is the number of quality pitchers that are in DIII vs. DI. Also in DIII you do not run across many LH pitchers or at least LH pitchers who have any velocity. I would say that a good DIII club that threw their ace could compete with any of the mid level DI's if the DI's were to throw their mid week guy.
There are mnay reasons kids choose to go to DIII, for some it is academic , for some it is because of size, etc. The only thing I can tell you is last weekend I seen a DIII player hit two grandslams off of a DI pitcher
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