I doubt it particularly matters which precise measure of simplicity I use, probably any reasonable measure will do.

You're too easy on yourself.

It's highly debatable whether it matters which measure of simplicity is in use, and it definitely matters that the one you use is precisely specified. Otherwise, I have nothing more to go on than, "Unknown said so" -- and I can't generalize to see if its use makes sense (satisfies some optimality criterion) beyond the limited case you're arguing for.