A few comment points from experience
I don't see the belt listed now on CC website but be careful when ordering and make sure there is an FIA time stamp on the belt. I've bought a set last year that didn't have it and that was a bad discovery to make.
Other comment is one I still havent found a solution to. Since replacing the belt, my seat doesn't go as far forward as it used to as the side belts jam in between the seat and the S3 chassis and stop the seat from going any more forward. Not a problem for many but my SO being of a shorter stature is unable to drive until I figure this out.
A seat job is one you want to do as little as possible. While simple in theory, on such a small chassis it's a huge PITA. It's a lot better with two people and it becomes a lot better if you find one of the DIY solutions to help the bolts stay in place for future replacements. Taking the seats in and out is also roughing up the leather on the center arm rest, which is an unpleasant result.
As far as other brands etc, others can chime in with that experience.
Edit: I'd like to add that I believe 6pt is pretty universally preferred to a 5pt setup.