If you never own a YS, you'll never know the true value of them. They really are superior to all the rest both in power and value.

YS63 is the same power as a Saito 82
YS1.10 is just a bit more power than a Saito 1.25
YS1.40 is just a bit more power than a Saito 1.80
I own all these engines and have compared the numbers and thrust.

All that said, when you compare the power/weight ratio, they are much closer.
I give the edge on fuel economy to YS for doing it with less displacement.