I have a set of Zipp 303 tubulars, and 404 clinchers.

The speed advantage of the 404's over conventional wheels is probably something around .2mph at 25mph

The weight advantage of CF tubular wheels will make a tiny difference in climbing speed. It will however make a noticeable difference in how the bike feels accelerating. The tubulars will also give a better ride and better handling, at least in my subjective judgement.

To me the biggest reason you'd go with CF rims as a non racer is just how nice they make the bike feel.

Between the 303's and the 404's I'd go with the 404's because the aero advantage trumps the weight, unless you're talking pure climbing.

The conundrum becomes tubulars versus clinchers. The tubulars will make the bike feel great, for the above stated reasons, but for me, are too big a PITA to justify if you don't have a wheel truck following you. But going with clincher 404's you'll get an aero advantage, but you won't get the great feel that comes with going to lighter wheels, and tubular tires.