I don't care for the serface skimmers personally...They look horrible and you can remove the serface build up in 5 minutes with a piece of paper towl floated in the tank once a month.
From a pruely mechanical standpoint...go with an AC but back it up with an air driven Hydro 3 or 4 for added bio-filtration. A Marineland emporer 400...(around $45.00 on line) ...can do both jobs efficiantly for less money.
Another option for a salt tank that I really like are the Skelter's (combination HOB filter and protien skimmer built in.) I used a few of them over the years and was fairly happy with them.