There are other airlines other than those two that only fly on Saturday, or they have more flights on the weekend. Plus by that time, there may be a ship or two again home porting in SXM, so there may be some charter flights also on Saturday. Definitely the airport is a lot more busy on the weekend. Check in desks at timeshares definitely should be less busy on Wednesday and you may be able to stay later in your room, if you ask someone nicely, when you go to check out. Definitely NO reason to pick the weekend when you don't have to!!