A while ago I researched this... Some studies have suggested that smaller keys permit easier "spanning" of octaves and improved reach, without materially increasing the chances of a wrong note. I think the study determined that a key about 87 to 94 percent as wide as a standard piano key benefitted players with small hands, without materially impairing those with larger hands. So some of you might actually be able to play better on the smaller keys of the Yamaha!
This comment only addresses key WIDTH. Not the length, throw depth, weight, firmness, velocity response, etc.
I love the idea of a "micro arranger." But I don't practice nearly enough as it is, so I didn't want to confuse my muscle memory by spending any length of time playing mini keys. IMO Korg threw away a golden opportunty, because that board had a lot of wasted space. They could have based it on the portable Kross battery-powered synth. It would have been 2.5" longer, and with 61 full-size keys!