subject to corrections by other cgn members, and it's been a while that i read up on the subject
nickel is suppose to be more "brittle" and not as soft as brass to reload over and over, that was the only downside, but i have never seen any peeling or loss of finish over time
but perhaps over the past 10 or 20 years, nickel should be improved by now in terms for reloading but i have never heard that nickel outlast brass, just prettier, always prefered the look of nickel, esp with the copper bullets
i think for 357 and 38, nickel for the extra few dollars would be my way to go, but buy both, you may want to distinguish regular 38 loads (brass) and 38+p (nickel)
wholesale sports in saskatoon selling lots of 38 brass for 2 dollars a box of 50, in nickel, but i think a good price would be under and up to $1.50 for 50, perhaps cheaper in bulk, saw ads lately on cgn for sale than that for lots of 1000
for semi auto calibers, i prefer nickel, for my old eyes, easier to find in the grass to pick out and pick up, lol