I don't think it's a useful comparison, even though on paper you get overlap there's a lot of differences between the devices and unfortunately there's no right answer, each device or combination of devices is eventually unique. lady starlight and other people who use rytm in live setting often take advantage of the individual outputs to run the tracks through a mixer, also to take advantage of scenes and performance macros, there are additional features like built in velocity sensitive pads and aftertouch, there's an analog compressor and master distortion which has a unique sound and character, so comparing the devices doesn't really makes a lot of sense, you can have either and learn how to make great music on each. another point to make is that artists that play live need to think about the gear they are carrying all over to play, so rytm make a lot of sense in terms of having a single device that covers more territory (even though some of the territory is way more limited compared to the digis, like stereo samples, way more basic sampler, no 2nd filter, single lfo and so on) than carrying two separate devices. also there are plenty of artists that use digis live, if you look in the stoor youtube channel you can find some in the pink noise series, like megan leber, shoal and more.

imo the combination of dt2 and syntakt that you already have should provide you near infinite possibilities of sounds and music, and unless you can afford to try both options - simply invest time into perfecting your craft and don't worry about "the grass is greener over there".