1 day wait lists are more likely to find a match.
What would you do if you get day 2 but not day 1 (or the opposite)
If you have a good backup plan, I would go with 1 day wait lists.
If you don't have a good plan, I'd wait list both days and choose a 2nd category as well...either way, might as well have 2 wait lists going.
If you choose 2 day wait lists, keep "stalking" the website and grab 1 day if it appears, then change the wait list to a 1 day wait list for the other.