If you’re not planning to use samples or sequence other external gear via MIDI then the OT seems like overkill. I think you would be better served by mastering the A4+AR combo. The performance mode of the A4 is great for pulling your sounds and sequences out of shape on-the-fly. I have every confidence that the AR will be equally well suited to performance.
Only if you hit restrictions on what you want to do should the OT be a consideration. Personally, I’d be more impressed and curious to see someone gigging with a combo that didn’t include an OT! 