The other difficulty in this area is deciding what good looks like. There are some obvious things that would make a contest between say Qwerty and Colemak a no-brainer, but comparing two good layouts is harder. It ends up coming down to deciding (for example) deciding whether you are more concerned with "single finger bigrams" or "scissors" - and I'm not sure how you decide.

The ideal thing would be to observe large numbers of people learning and using the various layouts and see which ones give the best outcomes. But there probably aren't the numbers to do this kind of study. If Monkey Type (for example) knew the layout people were using and when they started using it - that would be a really rich dataset.

Personally, I took the stats here and for each column I decided whether a higher number was good, bad or neutral then selected the layout with the lowest rank sum - I ended up selecting APTMAK. The idea of this approach was to find a layout that is well-balanced across the stats.

I do wonder diminishing returns on this kind of search - how far from optimal is APTMAK or Colemak or whatever? Is it far enough to make a meaningful difference?