[Pampered-Z]

Actually on a street car either one will be fairly close. Normally a SC kit cost less then a turbo, the STS kit brings the price closer, but I think a small SC like a P1SC or S-trim is still the better bang for the buck on a street car and stock bottom end. Now a turbo vrs a S.C. both at 6lbs of boost the turbo will yield more top end HP because boost if free where a SC takes HP to turn so some of the power it makes goes right back into turning it.

If your going with 15+ lbs of boost or all out racing then the turbo has more advantages, but then again at that boost level you need a motor strong enough to support the HP so your already digging way deep into your pockets!

As far as low end power, don't confuse a roots style with a centrifugal S.C.
A roots style SC moves far more air at low RPMS, which is why they are spun at much lower RPMS, and will make boost/power from idle.

The centrifugal SC like the P1SC or S-trim will start making boost around 2,500-3,000 RPMs, a turbo ( based on it's size ) again, I'm using a Small Sc and Small turbo for 6lbs of boost max., the turbo won't make the same boost until you get closer to 4,000 RPMs. So you feel the added power quicker on a SC, but turbo lag is not that much of an issue as it was years ago. The technology applied over the last decade has improved them, and the new motors rev pretty good already.