William,
Location wise Alana is much closer for me. Don't know what its like for you.
However, I would try Alexis first if I were you. Alana is great and you will have a lot of fun. But if you are going to have one of these as the base of comparison for future visits to other MPA's at other spas Alexis would be the best for that. Alana may spoil you to the point where you expect that type of experience from all MPA's. Alexis is more indicative of the other elites out there.
Regardless, you can't go wrong either way. Always keep an open mind with whatever MPA you see, let them lead the session and don't have super high expectations going and you'll be pleasantly surprised more often than you are disappointed.
Then go see the other one shortly thereafter.