i really like 135S for base white. havent been able to move up from that and get the vibrance i want, and ive tried changing basically all the other big variables.
We use 180S, typically for top spot colors over a base, or base whites with halftones.
I actually think we could get away with 3 mesh counts: 135S, 225S, and 300T (we would probably run a 310S or 330S if we had them). the 180S seems kind of like a middle ground mesh that doesnt really excel at anything in our shop. we stock and use them basically when we dont have enough of another count prepped and it can act as a middle ground for whites or colors.