Wet/Dry or Refugium?

[kaiser]

Well I am thinking about buying this hang-on-tank Refugium. It is 30" long, 12" tall, 4.5" deep. Will this be big enough for my 55g or should I get a regular wet/dry instead.
http://home.satx.rr.com/kfriedrichsen/images/35_3.jpg

[Tim Marvin]

I'd do the refugium over a wet dry.