In what ways? I've played with both at AES, but never actually used them.
I agree with TS-2000 for the following reasons
It has two receivers for VHF/UHF so you can be on HF/6m/VHF/UHF on the main VFO but still monitor and then switch over to the sub VFO to use VHF/UHF FM for repeaters while you are doing something else on the main band. The Yaesu 857/897 cannot do this at all.
There is crossband repeat, so you can use an HT coming in on 440 on the sub VFO and TX out on any other band aside from 440 on the main VFO....so you can come in on FM on 440 with an HT and out on SSB on HF.
There is a built-in TNC, a packet modem.
There is 50W output on 440 all modes, higher than the Yaesus.
The DSP is IF DSP, the Yaesu is AF, major effective difference....this is your filtering of received signals.
The audio is incredibly flexible from narrow to wide with EQ too, much more so than the Yaesus
The interface is a lot more clean as far as menu and controls than the Yaesus.
I own an FT857D and also a TS-2000 among others I own or have owned.
The 857 is a great low buck intro radio, but if you can swing it the TS-2000 is a lot more rig for the buck.
Of all the rigs I've owned and own, the TS-2000 is the one that won't leave unless Kenwood comes out with a new tech revised model with all the same features.
The Icom IC-9100 is coming out at some point, but it's missing a lot of the TS-2000's features and price isn't released yet....likely quite a bit more if I had to guess.