I'm biased, but I'll give you me story.
4 years ago, I was in the market of a blower, and couldn't decide on the Powerdyne or the Vortech. I talked to the manager of a local speed shop (he has powerdynes on his 94 Cobra, and his 98GT), and he told me all of the superchargers that he's installed on customers cars, at some point in time have needed a rebuild. But he's
never had to remove a Vortech to be rebuilt. That sold it for me - Vortech all the way.
To give you an ideal of Vortech's reliability, my A-trim (sn# 0435) had over 60K miles on it (40k from the previous owner), and it still kept on huffin and puffin. I recently sent it back to Vortech, not for a rebuild, but for an exchange to an SQ-trim.
As long as I own a Mustang, it'll be Vortech blown.
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TM88GT