I built a wood collar and put the taps on the side (rather than the front; it was better for the room that the keezer is in). I used this setup, rather than a tower, for a few reasons. Firstly, I have read that towers can be a little harder to keep chilled on the last stretch of beer line (which can be fixed with a well-placed fan, but not to the extent of a collar setup). This isn't as major of an issue with collars (esp. if you have a little fan in place). Secondly, and most important for my needs, I wanted the freezer top to be free for storage, etc. I can put glassware on top during a party, or snacks, or whatever. You can also open up the top to change kegs more easily with a collar; as you note, you may have to move the whole keezer out from the wall (depending on placement) with a tower.
Disadvantages of a collar is that you definitely have to do a bit of monkeying with lid removal and placement, etc., and it can be harder to deal with drip trays (but quite workable -- I glued mine on the side). The other disadvantage is that you have stuff projecting out the side, which can be a hazard if you have lots of traffic near the keezer (e.g., small kids).
If I were to do it again, I would still go with a collar/taps out the side. For my situation, it has been pretty good.