I've had them both, so I may be able to answer.
I LOVED my Vortech V-1. No one ever mistaked it for anything but a blower at idle. It has a very, very nice whistle at idle. If you're looking for a track car with a blower that can grow with your car, the Vortech is it. It's cheap and can go far. You'll want deeper gears though to get the blower into boost quicker. Running 4.10s with my long, long road trips wasn't my cup of tea.
The SVO is fairly quiet at idle, but really starts to whine when you get on it. The SVO is good if you want an ultra-reliable street blower. It'll really wake your car up (even with stock gears).
I do mostly street driving with the occaisional strip pass. That's why I swapped blowers. I've done a lot this winter to try to make this car quicker than when I had the Vortech, but more streetable. We'll see if I've succeeded.
BTW, I have 60Kish on my car.
Tim