Since I have dual VP150 (the one below firing straight, belly-level and the one above slightly pointing downwards about a foot or so above the head), I would now tend to vote on the dispersion of dual-centers over a single M80. Sounds is still very directionnal to satisfy dialog and character movements, but evenly distributed accross all my seating positions.
I wasn't talking about dual 150s, there is something unique to a dual center set up, dialogue is very centered to the screen, IMO. But I still feel the M80 as a center adds more dynamic range to the whole experience and still has a wider dispersion than dual VP's, but I am going on my testing of dual VP's (a 100 and 150) compared to an M80 not dual 150s.
