I've had both styles of tensioner on my truck and each has failed. The shock version did seem to chirp the belt when it was cold a little more than the non-shock version. The only thing I can tell you for sure is that neither is designed heavy enough for the 7.3 application. That's a pretty good price, however, keep in mind that any Ford dealership should warranty a new tensioner for one year, which you won't get on FleaBay.
I have also heard some folks claim that NAPA sells a tensioner that seems to works better, but I can't confirm it. All I can say about the Ford version is no matter which one you run, both are failure prone, so pay attention to belt squeal so you can replace it before it comes apart and takes the belt and idler pulley with it (no, the dealer won't replace those parts if they get taken out with the tensioner).
Good luck
R. J.