You wear NWUs during OC phase now that wash khakis and winter blues are gone. Personally, I found them pretty comfortable, but I've never worn wash khakis as a frame of reference. Just make sure you get properly sized on your uniform fitting. I let the nice ladies at the NEX talk me into Large-Long for both blouse and pants. I'm 5'9" and 180lbs. Those things were HUGE on me. I bought a pair of Mediums here in PCola on the off chance I have to wear them. So buy what fits. Oh, and only wear one pair while there. Multiple trips to the rosegarden/SUYA/etc will ruin most of the things you wear during OC phase. Keep the other two in good shape. You can spill ribs/spaghetti/sand/sweat/piss/blood on NWUs and they don't show it. Just wash em 2x/week and you'll be set.
They don't look as sharp as Service Khakis, but much easier to keep up and actually do work. I wish we could wear the desert style, but that will never happen unless I wind up in Azzcrackastan.