When I first started reloading almost three years ago I submitted four different orders here and there, just to get my hands on some .357 brass. After waiting for about two or three weeks, all four of them were filled within a week IIRC- Winchester, R-P, Starline and some PMC.
In my opinion Starline takes the cake: best price and excellent quality. The Winchester's were the most expensive and I do not think the extra cost was worth it, though they do shine up real nicely. The R-P's aren't too bad, the PMC... meh.
I lost count but I think I have about 5,000 pieces of .357, with about 60% of that in circulation. Maybe I should order some more