It would depend what you want to put into the tower.
I started off with a bog standard A1200, started upgrading and went the tower route. As people say, it does seems to lose its charm, but that's why I bought another A1200 years later ;-)
I have two towers now (a Power Tower and an EZ Tower) containing a Mediator, FastATA and PPC card etc and the other with a BVision, etc.
I recently stuck the second PPC card I have in a tower and am planning on customising it (i.e paint it black, get the dremel on it and make it personal to me).
All good fun, whichever route you choose :-D
Steve