I purchased an Apple Watch that came with the nylon band and I had to go get the other sport fluoroelastomer band for working out because that nylon chafed the crap out of my wrist. I tried using a topical steroid after workouts, alternating wrists, using anti-chafing products, no go. If you workout low intensity, I can see how it might not bother you, but once my wrist got sweaty, the nylon band was horrible. Also, the nylon band holds water (and sweat) taking awhile to dry.
I do "other" for weightlifting, and pair my watch to my Polar H7 heart rate monitor chest strap. Otherwise once my wrist got sweaty, the Apple Watch HR sensor was saying "145, 72, 123, 180, 30, 54" like no joke how terribly inaccurate it was. It also takes forever to update readings whereas my chest strap provides constant readings. Regarding the calorie calculations, no way that's close to accurate. I've been gaining weight (bulking on purpose), yet if I used my daily myfitnesspal dietary calorie total and subtracted the calories from the workout plus walking calories burned and also subtracted my predicted basal metabolic calories burned, I'd be way negative.