Switch From United
 

I'm looking to switch my mileage earning to a different carrier from united to try and take advantage of the star alliance award upgrades that I would be able to use my miles for if I were in another program. Which program would you recommend, I fly mostly domestic on united, and economy plus is nice, but its getting ridiculous with the use of miles for international flights.

It depends on where you want to go frequently intl, if Asia you can try SQ, across the Atlantic LH. Domesticly there is always US.

Domestically, there is never US.

I was wondering more in terms of keeping my miles without them expiring and being able to upgrade across the star alliance.

Having miles without expiration and upgrade on *A?
I guess you're best bet would be M&M.