both have their obvious pros and cons.
baseball, your hand would be contoured around the neck, so its better for your hands, and i would assume your wrist, arm, etc. you can also do some fun bassline stuff on the low E.
classical, you can travel all over the neck easier. its better for fast runs. buttt after a long time, it can start cramping your hand- especially when your streatching alot with your pinky.
you can go fast with baseball too, but its just not as good for traveling up and down the neck. you can go very fast in one place on the fretboard.
what i tend to do is when i do a long run up and down in one place on the fretboard, ill do a half baseball half clasical hand position. so my thumb is almost all the way around, but theres still some space between my palm and the neck.