One thing missing from outboard is the OT scenes manipulation power… & if no midi on external fx, then no p-locks or lfo action. Also only 4 outputs on the OT is a big limitation with wanting fx per track. Hopefully Elektron will add more fx via OS updates as time passes.
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For affordable, thumbs up to the zoom g3 which is awesome, really nice amp sims, modulation fx & delays/reverbs, been really good for some old synths. Based off that, I just ordered the Zoom MS-100BT (Zoom MS70CDR good also but doesnt have amp sims, distortions or bluetooth upgrades) for stereo inputs & even smaller footprint. Will be used via the OT Cue outputs going into the MD for resampling there, then back into OT.

In saying that i have an external portable rack that goes everywhere with my elektrons. No modulation fx but much post processing.