The main thing I find I miss when writing on the OT, or any Elektron device over a DAW is sequencing automation that is longer than 64 steps. So nice on a DAW to be able to daw those nice big curves.
Also because you can't separate out the tracks in the arranger, having to duplicate heaps of patterns just to get small variations.
Though that's easier on the OT because you can have clock divided tracks to let them run over a longer time. (so wish the RYTM had that)