After having several dozen RIOs and CAPs in various tanks over the years (I have a set-up & maint. business), I toss my vote in the ring that rios are garbage and caps are pretty good. Of the caps I have running now, a few have developed rattles after a year or so in constant operation, but I'm willing to write that off to not running them with a prefilter (they're being used as circulation pumps) and having them ingest debris from the tank. On the other hand, nearly every rio I've ever owned has failed spectacularly, filling the water with toxic chemicals, electrically charging the water, etc.
Get a cap if you want; for the money they're decent pumps. But **please** take my advice and never buy a rio. Not only are they terrible pumps, but the company behind them is terrible, too. Put it this way: I had to call the BBB just to get a phone number for them! Taam (the parent company of rio) doesn't list their phone number anywhere, and they don't answer faxes or emails (when I finally spoke to the owner of the company on the phone, he told me this directly).
-John
