OT Pros:
crossfader, scenes, far superior modular FX system, live looping, track scale per track (superior sequencer overall imo), 4 input mixer
DT Pros:
Better fidelity/resolution sampling engine, tempo per pattern, i feel less bad about smacking the keys and spinning the encoders like a caffeine injected dataline, oled screen (at least vs mk1), OB is the business (shout outs beta testers)
owning DT & OT together frees up the OT to do more live sample mangling or processing of external signals with neighbor tracks etc. leaving the DT for bread and butter sample playback.
i own both, i could live with out the DT but not with out the OT.