Meh tuners are just convenient, love me TU2
Dunno about DT so much, but I've had both Whammy 4 and 5
Whammy 5 does everything the 4 does, except it doesn't have the dry output as well as wet, but I never used it anyway.
Whammy 5 unlike the 4 has true bypass, runs on 9V DC so is more compatible with most power bricks, has the polyphonic chords mode
and looks sxc
If you can get a Whammy 5 for a decent price I'd get that. I got one off US eBay (cheers James oxoxoxo) for cheap, but customs can be a dick