In view of your location, I would suggest signing up for United's program. If you also register a credit card with their dining program (any credit card that is not registered with a different airline's dining program), it's easy to keep your miles active even if you rarely fly UA or its partners. Before you take any action, however, it would be wise to visit the UA website, go to the section on earning miles on partner airlines, and make sure that your TK ticket is in a class eligible for earning miles on UA.