I've switched between AC, LH, UA over the years depending more on my anticpated travel patterns than my location. I have been using UA as my primary and LH as my secondary for a few years now, although I very rarely fly UA long haul. Besides UA I fly LH and LX with some regularity, AC and BD (as well as the Baby product which does nothing mileagewise), and then assorted other *A carriers depending on routes.

I also keep miles in my AC account.

UA for E+, LH for mileage upgrades, AC for lower mileage requirements. Taxes and fees on award travel are definitely an issue, so I spend my miles wisely.

However AC and LH are also changing more than UA is changing so I would look at various programs carefully and their recent and upcoming changes before making a decision.

Other than that, being a non-US UA customer can be annoying at times. There are a few threads in regards to that here. Others would say that we receive 'better' benefits than US based customers, but I am not yet convinced of that fact.