loose footed or track mainsail
I personally prefer a loose footed mainsail to a bolt roped shelf foot. The loose footed sail is adjustable through a wider range of adjustment and is substantially easier to remove from the boom. Properly cut, a loose footed sail does not require a flattening reef. For racing the loose footed sail gets a tiny amount of unrated additional sail area. I have not noticed any difference in ease of flaking or durability between the two(although the shelf foots can quickly get pretty beat up and stretched out).