I, too, have a P30LS. I personally ride both (carrying cocked and locked). Thumb between hammer and slide, while the trigger finger rides against the safety. It does compromise my grip slightly, but it's not a huge deal, IMO, particularly since I'm holstering, which suggests that I've decided that there were no more threats in the area. If I was choosing between just one or the other, I would also opt for hammer rather than safety. As BOM noted, the safety can fail, but riding the hammer will insure that the gun won't go off.