Good topic! Now that the older siblings with egos are off fighting it out about who is tougher; the little kids can come out and play.
As younger and smaller children, both ranges tend to get overlooked and ignored by most adults. That is often a good thing. It allows us more freedom to do our own thing and have more fun. Both ranges have their peak lists, but they are all more laid back and less stressful. Perhaps the Greens are a bit more laid back, but Cats are cool and feign disinterest in such matters.
Compared to the big boys, both ranges have more round green hills which may be shorter, but they are tall enough. The Long Trail, Long Path, and other long traverses in both ranges can kick butts.
The Greens get more snow and have more skiing. The Cats have less mud and fewer bugs.
Some peaks in the Greens are more lofty with alpine zones. The Cats have tend to have more wild streams, deep cloves, and tall waterfalls.
The Greens have awesome color in the autumn. The Cats can throw a good hissy fit during thunder storms, and who doesn't enjoy watching a good cat fight.
It is a close call, and there is probably no right answer. But I will temporarily even the score by voting for the Cats. We Cats are loyal; even if it is not always obvious to the casual observer.