on a normal gibson the center block doesn't even really touch the top or bottom, and on something like a 335 there is not a HUGE difference, but there is definitly a difference,
i played jeromys epi dot and then the one i made for him side to side and the one i made for him is much heavier and has a better all around balance in terms of acoustic quilities, electric quilities and just being able to have a strap on it without it diving at the neck end.
i have also played a tru carved hollow body(1940's something epiphone, new york factory) and a number of laminent hollows.
and there is a huge difference in sound, a laminent sounds really...... thin to me compared to the epi i played,
but then again, the wood is 60+ years old and it has had time to "settle" quit nicely.