What kind of setup are you looking at?
In marine setups, UGF still work, but limit you to using larger substrates, which can cause problems. Running it RUGF with good pre-filtration resolves some of these: reduces the wastes trapped in the sandbed, but increases the maintenance you'll have to do to keep the pre-filter clean and functional. Ditto the pre-filter for a wet-dry. To be honest, either will work, and many swear by them, but IMO, live rock and sand, along with the appropriate critters, is a much better, lower maintenance option.
