I built my iris some time ago and have to say that it's lot of fun to use. Price was also pretty good in this genre but of course it's DIY asset. Limited size makes work qualified layout creation challenging but I hope to nail it soon...
I use a Kinesis Advantage and while it is not split, it does have concave key wells which in my opinion is superior to the flat ones on ErgoDox. The middle section is large enough to fit a Magic Trackpad 2 and I have seen people mod their keyboard to place a wireless charger beneath.
The Kinesis Freestyle has a mechanical version (https://amzn.to/2Emhout). I'm typing on it right now. I wonder how the author would have assessed the Kinesis if he had tried the mechanical version.
There is a substantial difference in price, although the mechanical Kinesis costs less than what I paid for the regular Kinesis several years ago (prices have come down quite a bit). More importantly, years ago when I tried the regular Kinesis the mushy keys were unacceptable. It takes a fair amount of time/practice to acclimate to a split keyboard and I wasn't willing to do that for a non-mechanical keyboard; the mechanical version removes that obstacle.
https://keeb.io/products/iris-keyboard-split-ergonomic-keybo...