I really like the MOTU, I feel like a shill because I've been recommending it so much. There is some more info in the review thread about my experience with it but as I also have an Okto it might be appropriate to make a few comments comparing the two.
The MOTU output (8.6 V) is hotter than the Okto (4.2 V), as my NC252MP amplifiers have normal input sensitivity (1.7 V) line level attenuators are probably warranted especially if using volume control upstream of the DSP.
The Okto is just a bit quieter than the MOTU but neither have any audible noise once you get a foot away from the speaker.
10 channel output from the MOTU is really nice and would be perfect for a 4 way + sub or a 3 way + sub where you are bridging a Hypex amplifier for the sub and want a + / - output to the sub amp.
The biggest differences are price and usability. The Okto is great in that it has 5 V trigger output, bigger volume knob, bigger display and IR receiver for remote control. You can definitely work around these issues with the MOTU but it definitely adds cost / complexity.
I have found that a Bobwire DAT1 can be used to add a trigger output as the MOTU does have a TOSLINK output. I really like that the MOTU has TOSLINK and SPDIF inputs as these are obviously much more prevalent in consumer gear than the Okto AES inputs. MOTU works great with a RPi4 running Ubuntu Server / CamillaDSP.
I really wish the MOTU had an IR receiver for volume control which is probably my biggest compliant. You can get around this if you use upstream volume control, there are plenty of DIY solutions for this especially if you are using a RPi / CamillaDSP but that adds complexity and is not for everyone especially if you want a "finished" looking solution. I am currently using a SHD Studio with the MOTU as it provides good input switching functionality and volume control although it is super expensive for just that functionality. Would love to find something much lower cost that has decent input functionality, a nice display, IR receiver and digital volume control to use upstream of the MOTU. All that being said the Okto is quite a bit more expensive (and unavailable) so it somewhat offsets. Looking at my setup with the Okto which uses a DIY miniSHARC with 8 channels of AES output the total cost is upwards of $2K so if you compare to a SHD Studio ($900) + MOTU ($600) + RPi4 w/ PSU ($70) + Bobwire DAT1 ($70) you end up at just over $1600 total and have more input functionality, more outputs and Dirac.
I mentioned it a bit but the Okto has non-deterministic delay between channels (between 1 and 2 samples) when using the AES inputs which is super annoying. This can be accounted for in DSP but if you power cycle the DSP, power cycle the Okto or switch the Okto from Pure AES to Pure USB back to Pure AES these delays can change. Fortunately it is super easy to measure these delays with just the Okto itself. I haven't actually done the same testing with the MOTU yet so it will be interesting to see if it has any issues in that regard, especially given that it uses two DAC chips.
Michael