Most of my typing is in emacs, so having the ctrl/alt modifiers on the thumb clusters was important for me; it lets me navigate easily without moving my fingers much.
Here’s Jashe Poon getting 158 wpm on a test where his keyboard layout suddenly switches twice so that he ends up typing 20 seconds each of Qwerty, Colemak, and Dvorak: https://m.youtube.com/watch?v=GK8UQGO-qFA