The only promotion I'm aware of is a possible UA promotion, due to the partnership between UA and Marriott. See here:

http://www.flyertalk.com/forum/marri...wardsplus.html

and here:

http://www.flyertalk.com/forum/marri...announced.html

And for promotions in general, check this thread, which is always near the top of the first page (ie, "sticky"):

http://www.flyertalk.com/forum/marri...ks-promos.html


... Knowing nothing about you (what airline to transfer to is likely to be a personal choice, based on things like where you're based, which airlines you already collect with, where you want to fly with the miles, etc, etc), I can't guess which airline would better.