I recently received my SVS PB1-ISD sub, and have just started putting it through its paces. For first impressions, it is an excellent sub. I had read that you don't just 'hear' an SVS sub, but also 'feel' an SVS sub. I can say that for both movies and music, that seems to be true.
The impact this sub brings to movies is astounding. I have tested scenes from LOTR, Fight CLub (mid-air collision!), Monsters, Inc., etc., and this sub really comes through with low, clean bass. I haven't really had enough time to listen to a full range of music, nor to confirm I have it calibrated ideally for music yet, but for my initial listening, it performs very well for music. Bass notes are clean, and seem to relay what they are supposed to. Bass guitar sounds like bass guitar, bass drum sounds like bass drum.
I didn't have the chance to listen to HSU subs, but of course it came down to those 2 brands. When it came time to choose, the shear magnitude of praise for SVS, as well as the excellent customer service I received during the research phase, sold me (in addition to the features of the PB1 of course). As SPiffy confirms though, you really can't go wrong with either brand.
