WH or low sec?
WH, by a wide margin. Unless the scarcity era changed something very drastically.
LS. unless you have ability to farm C320
Even if you ignore isk/m3 (which is in favor of LS anyway). There is more variation in LS gas so you can easily split your volume and have easier time to not flood the market
Cyto gas found in certain areas of NS is the most valuable gas iirc
Nowadays it’s low sec. Cyto is generally worth more than myko.