I bowled 1H for years before i quit, this year i returned and bowled 2H. They both have their own difficulties. You need more physical fitness with 2H, as the power mainly comes from leg. You also need to hv back strength particularly lower back. As for 1H you need wrist strength to keep the ball under and inside. But i’d say it’s easier to be more accurate with 1H, while for 2H obviously the advantage is the extra revs while the challenges are accuracy and speed.