A lot of the brass you buy now the case mouth needs to be sized because some are dented and out of round.
+1
As for the remington vs. winchester debate.
Both are "bulk" brass of average quality. I wouldn't rate one over the other, as they both vary quite a bit in overall length and case volume--even between pieces of the same lot number. Good for most shooting needs. Buy whatever it cheaper.
I tend to use mostly winchester for pistol and rifle...not because it is superior, but because it is most available in my area. Also, I tend to stay away from Remington pistol ammunition becasue I find it seems to run a little dirty...so most of my pistol brass is winchester. Once I develope a load, I like to stay with the same brass.
