Usually full, but if I know that it's going to be a relatively short pull (with no TT bathroom breaks) than I will pull empty. Pulled with less than half tank once on a trip where we KNEW we were doing one overnight in a truck stop parking lot. Had more than enough water for flushes, hand washing, and other minor use. Trouble was that that the other couple we were with had a breakdown, and I got FILTHY making the repair, and didn't have enough water for a quick shower. Fortunately, the truck stop had showers for the drivers, so I showered there. They have since added an RV Island, so RV's can dump, flush, pull forward, and fill!
2014 RAM 2500 Laramie 4x4 Quad Cab w/Cummins Turbo Diesel, 2009 Rockwood 2607, and 3 'yaks!
300W of Suntech Solar, a Rogue MPT-3024 Controller, and a Xantrex PW2000 Inverter