my firsthand experience.
I had a 350z with a stillen (magnuson M62) stage 3 supercharger
I also installed 2 Vortech superchargers on friends cars, a 350z and a G35.
I really, really liked the performance of the stillen, although the total output and performance potential was a lot lower than the others.
I got about 340 rwhp while they got around 420, but I had 90% of my max torque and hp at 1800 rpms. It was perfect for track days.
So, I would say that for a daily driver, track day type car, I would go with the maggie again. For drag racing or just bragging rights, the centrifugal or turbos. The maggies just aren't real upgradeable.
All of this being said, I just bought a Vortech kit for my C6, but thats because 1. it was on sale in a group buy for an unbelievable price, and 2. my 240z is my track car, or will be as soon as its running properly again.