Probably cwc, I feel like it was a fun zone and there wasnt a large amount of bs with that patch other than frag losing its stun and the nerf to offbalance.
The last time I could play without crashing multiple times when approaching large fights in PC/NA Vivec was probably sometime between Morrowind and Summerset.
Late Trueflame and Early Vivec were laggy as heck, but performance wasn't quite as bad, with more players, and we didn't have to run on foot from Chalman to BRK because we were stuck in combat.