I suppose on the one hand, attending second look at the school you're less excited about would give you the opportunity to learn more about the school, the area, and your fellow accepted students, so that you could make a better-informed opinion. You might find out that you like the school better than you thought. However, I have heard that revisits are not always the best way to judge the vibes of a school, so ymmv.
On the other hand, attending second look for the school you're most excited about would also give you the chance to network with other accepted students, look for housing, and get to know the city. It would be more of a way to start orienting yourself to the school than trying to learn something new. I would think if you're really excited about the program, second look is unlikely to change your opinion towards the negative.
If you get financial aid information before the second looks are scheduled, that would obviously be optimal as it would help you decide. If you don't, I'd consider this: would significant aid at the school you like less be enough to make you consider going there? If yes, maybe give them another chance at second look.
I'm also in the predicament of having two second looks on the same weekend, and I havr chosen to go to the school I liked less to give them another shot.
It is a tough choice, I wish you luck!