completely anecdotally (sample size of one!) but I found big improvement in comfort and posture when i moved to the kinesis ergo (split, but joined) about 15 years ago.

Eventually I moved to a full split, positioned quite some distance apart (~25cm) and found that even more comfortable.

Always hard to know with stuff like this if you are just imagining it, but for various reasons, I'm pretty convinced it was an improvement for me.