I can tell you that we sell both lots of different types of turbos, but the most popular, and the one getting the most rave reviews is the SP 62 if only seconded by the SP 66. Every customer we have that has purchased one, and has in the past had other types of aftermarket turbo, has over and over again told us how much better the 62 is. It seems to be doing good for the guys that tow any amount, to guys that race the ricer at the light, to your daily driving lightfooted people (as if there are many of those), this thing just seems to hit the nail on the head.
I am not trying to push one product over another, this is just what I have seen with my eyes and heard with my ears. To each there own.
Russell