The sun factor is something I hadn't mentioned. I'd never had any issues until the last couple of years, when my legs started burning in early spring weather, when it was still cool. (Previously, they just tanned nicely; more of those getting-older compromises!) So, not only will they help in cooler weather, but they'll also allow me to expose my legs gradually to the sun.

I'll have to check the weight, too. I suppose I could deduct the weight of a pair of shorts from the zip-offs, and be close enough on the weight of the legs.

I was leaning toward non-zips, just because of my general bias toward simpler-is-better, but I wanted to get other opinions, too, before making up my mind.