All down to a matter of taste. I found the Mexicana lounge shabby and overcrowded. If there was waiter service, it wasn't on the day(s) that I visited. The AAdmirals Club is nothing to get excited about, but feels a little more spacious, and the barman is something of an Anglophile.

Incidentally, if the three drinks chits are insufficient, you can ask for more at the front desk.