IME and O, in terms of price from cheapest upwards:
1. Red Sea Prizm: poor reputation
2. Marineland Seaclone: poor poor poor reputation (called the "Sea Clown")
3. Coralife Superskimmer: does well, good bang for buck but honkin' big
4. CPR Bakpak: not bad, some people like, some hate
5. AquaC Remora + Pro: generally good, some swear by it (like me), a few hate it
6. Deltec: Holy Grail of HOT skimmers if only you could afford it.
Best "bang for buck" would probably be the Coralife. Too bad it's so big and ungainly looking. The AquaC works well and is mininalist-looking and svelte but can produce a rushing/gurgling sound. This can be minimized by a simple mod involving folding up a paper towel or two. The Deltec skims the crap out of your tank (literally) and is unobtrusive. Too bad you'll be short some limbs if you buy it - fantastic if you find a used one in good shape.