It's a nice pair.
I use both live and in studio.
You can create great and crazy sound in ND2 with lots of variation by using P lock and CC.
As MichalHo wrote, the only limitation is one out only and no FX on boards.
I sample static sounds on OT from ND2 (as kick for example) and I play dry with audio track and the rest in MIDI so I can work in the synth section of ND2 for real time modifications and add EFX also from OT.
BTW ND2 is very different from AR, not only because one is a module and the other is drum machine.
ND2 can produce a very big range of sounds: percussions (synth or real like), synthesizers and abstract sounds that I really love.
AR is a great machine but more limitated in sound design way.
ND2 sounds digital (It's characteristic and not a problem), AR sounds fat and more (for me) wild.