I've always hated towers because they take up more room. Sure the footprint of the case is smaller, but who didn't stack their monitor on top of the desktop unit? Ergnomically, you want the monitor at eyeball height anyway. Unless you're not adult-sized, you need something to raise the monitor.

The funniest things I've see are people with towers and they have monitor risers to raise the monitor by about the same height as a standard case.

These days, with 20+ inch monitors, the monitor takes more space than the CPU anyway. Put a tower beside the monitor and it's even worse.