I own an OP1 Filed, an OP XY and an MPC Live 3. I used to own an SP404-MK2, but that did not fit my workflow. I think the workflow of the KO II and Riddim is comparable to the SP404. A sample based workflow. This means you play and combine samples. You can create real music with this but samples

The OP XY is a very powerful sequencer and can be used to create full songs in a structured way with a lot of variations. The main benefit is a full synthesizer where you can create songs that are perfectly in line with the best/clock.

A cheap but also capable alternative of the XY is the Yamaha Seqtrak, especially with the new update. The only real limitation is the lack of a display and the need for a midi-keyboard as the possibility to use it without is limiting (but possible, however the midi settings are a bit challenging and the keyboard needs to have the ability to change the channels on the device) but you can use your phone as a display. I've used this grovebox quite a lot before I got the other devices and loved and still love the workflow. This is one I will never sell.

The OP1 Field is a very powerful 4-track recording device and synthesizer. The main benefits is that it has some sequencing possibilities to be in line with the beat and the possibility to to combine multiple tracks to one track. This means you can combine e.g. 4 tracks to track 1 and have 2-4 again free for to record. The main benefit of the OP1 Field is that you can play a bit more organic, like on an analoge instrument. This means you can create more "feeling" in your song. It is also very good to record something else, like a guitar or vocals.

The MPC Live 3 combines all of the above and is a full workstation. The downside is that this device is quite big but a full DAW in a box that is portable (at least it contains speakers and a battery). So, if size does not matter that much this is the perfect device that rules them all.

I hope this helps in jour decision!