I have an ssqv (hks) at the moment, but I'm pretty sure I'm going to ditch it for a synapse synchronic. All i've heard is good things about them...
...and operation should be all that you're concerned about when purchasing a BOV. Not sound. I purchased the ssqv because it was simple (didn't require too much adjustment as many do) and I got a deal on it that was well within my price range.
Of course, I had an RFL before that, which I hated.
The more you modify your car, the less you care about "sound" and more you care about performance.
At least, that's my opinion, anyway.