Premiership. I think even he knows that the World Cup is a bridge too far for England, particularly since he's always been assigned a peripheral role because Lampard was perceived as "better". So deep down I think he wants the Premiership more, because it's the one he's been closest to winning and is what Liverpool-born players most want to do - bring home the title that's eluded us so long.
A few years ago it could be said that Gerrard's heart was on his career more than on his career with Liverpool, but I reckon he's 100% Red now.