The tonal balance between the two is reported to be pretty much identical. The main issue seems to be how far you will be sitting from the center -- if it's a compact arrangement (say 8-10 feet) then VP100 is fine, but if your seating distance is getting up into the 12+ foot range then VP150. The difference is ability to play loudly and clearly more than the timbre of the sound you get.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8