Well no one replied so I will give it a stab.
A sump is a great addition to your 55 gal tank. I personally run sumps on both my tanks and like them a lot.
What are your plans for your reef tank ?
Just corals - no fish - corals and fish, LR and fish, .....etc.
Once you know your "plan" you may find it easier to decide and get more replys here
For a reef with corals and a couple of reef safe fish, if you are using a lot of live rock - 50 pounds plus, and a deep live sandbed and clean up crew, then I would not use the wet/dry.
Just get a good protein skimmer in your sump, check your water often and do necessary water changes.
If you are going to have a lot of fish - and not going with a lot of LR and sand, then get the wet/dry.
I could go on like this for a long time, with various combinations and set-ups, so why don't you let us know what you are planning on down the road with your 55, and I'm sure we can offer some replys.
Brian