How frequently do you cross-chain? Or more precisely, how confident are you that you will never ever cross-chain even by accident? Total wrap capacity should be the difference between little-little and big-big, neither of which you want to use intentionally.

I select chain lengths for two criteria: 1. So that the derailleur is stretched but not to a breaking point in the big-big combination; 2. So that the cage isn't wrapped all the way backwards in the little-little combination. The first of these is more likely to break something and more likely for me to hit accidentally, so I err on the side of a longer chain. If the RD can't handle those extremes to my satisfaction then I look for a different RD or different gear combinations. But since I like long-cage RDs anyway this is rarely a problem.

Yeah, I know, that didn't answer your questions.