Easier passes all day long. Every successful change to my waterskiing in the past 5 years has been from working on things at my easiest pass, and _slowly_ working the changes up into harder passes. Running deliberate, smooth passes is hard at all line lengths and all speeds, and to often I see skiers ignore flaws at their opening passes just because they ran the pass and weren't feeling rushed. That said, you do have to keep the feel of your hard passes, plus they tend to make your flaws obvious, giving you something to work on.