Gerrard is better than Lampard if you ask me, at least at their best. Bear in mind one has been playing in one of the best squads in history while the other has been playing for Liverpool.
Lampards stats are a little misleading too, a huge number of his goals last season for example came from penalties, and a large number of his assists come from set plays.
Gerrard has much more in his locker, probably more erratic too which is what lets him down, but on his day he's an absolute beast.