Maybe it's obvious, or not...but one's preferences may have driven by the type of tone you like, as well as by the type of interface you like and how much you enjoy tweaking.
I have not tried any of them, and am not really in the market for a compact Class D. But I have done a fair amount of reading about the line. If I was in the market, the only one I would really take off the table is the D800. Why? My impression is the D800+ does everything the D800 does and more. People who chose the D800 tend to like the simpler user interface and also prefer a darker tone. The + has more controls/features, and can also be setup to sound brighter. I like the ability to teak and I like a brighter sound. I would definitely pay the small price premium for the extra features and ability to dial in the tone I prefer.
The user interface I find most intriguing is the WD800. I actually love to tweak and this amp gives you lot's of power and flexibility. I tried a Walkbout and found it too squishy and underpowered for my taste. The WD is supposed to overcome these perceived "limitations" with lot's of power, variable HPF, and the power amp damping control.
I am sort of luke warm on the TT800 conceptually, but I recently bought a D180 and I have had a surprisingly long honeymoon with it, so maybe I shouldn't be so quick to write off the Boogie channel.
Obviously the best thing would be to try all of them out for yourself; of course that's not always reasonable.
Good Luck!