I've got an an answer that will hopefully clear up this question once and for all. (Yeah, right.
)
The main difference between the vp150 and the vp100 is the width of the sweet spot they produce. By sweet spot, I mean the horizontal area over which the high frequency response remains relatively flat. Outside this zone, the highs will roll off and detail will be lost.
Because its single tweeter is flanked by woofers (an arrangement a.k.a. MTM or D'Appolito), the VP100 projects a more focused sweet spot. This makes it better suited for smaller rooms where the viewers/listeners will be more or less directly in front of the screen.
The VP150, on the other hand, has its tweeters to the outsides, flanking 3 woofers (a TMMMT arrangement). This creates a much wider sweet spot, making the speaker suitable for larger rooms or rooms where viewers/listeners are more spread out.
It is my understanding, however, that to a viewer/listener positioned directly in front of either speaker, the sound is very similar.
