I have both, and they are very different beasts with much less in common than the huge amount of differences.
Taking samples on the Octatrack for me is much better in almost every way, you can easily and quickly (once familiar with basic operation) take a sample, normalise it, trim it, cut bits out, reverse parts, add or subtract gain, etc etc. You can easily retake a sample again, quickly save it and or multiple variations of it.
Deluge sampling is a bit more basic, everything is automatically saved since it samples direct to card, no destructive editing possible on the Deluge, I also find it a bit to easy to accidentally mash play and rec and inadvertently start sampling, a real pain when not wanted. The upside being that it is super simple to record a whole song direct to audio.
Playback of samples: Both sound excellent, Octatrack is by far the better mangle the bejezus out of your sample or juggle them around or realtime manipulate etc, but Deluge has polyphony, better pitch range, multisampling, kit sampling, and as many samples loaded as you could reasonably need, it also handles large samples.
Sequencing: Octatrack sequences samples in a much more comprehensive way, full control per step over pretty much everything, midi sequencing is much more basic than the Deluge though, the Deluge grid makes rapid experimentation of note and position super easy and quick.
P-Locks and trig conditions: Both handle these on about par, though the OT makes it easier to view what values are on a step.
FX: OT has more variety and better sounding FX, Deluge has more simultaneous FX.
Building a song: Both very different in the approach but both very capable, Deluge arranger is very good but can suffer from a bit of LED fatigue when things get complex, OT can be a bit fiddly if wanting to do complex arrangements, both though seem to give good compromise between power and usability given their interfaces.
Performance: Quite different in the approach again, OT has scenes and crossfader, trig modes, fills etc. Deluge focusses more on moving between sections, muting and trackwise or all track manipulation of parameters. OT can realtime resample, mix external, and so on, Deluge can use line in and realtime repitch and generally filter and fx incoming audio but obviously only on the 2 inputs.
It will be interesting to see how the Deluge looper is implemented.