Based on the performance of samsung's other products my expectation is the 3d on the 550 will likely be better than the UT. Of course, this is all speculation based on reviews and not actual observations.
In 2d, I would expect the UT to trounce the 550. Again-- speculation, but unless Samsung has dramatically increased the quality of their entry level line the UT50 looks to be the hands down favorite amongst the budget videophile crowd. Personally, the UT makes me wish I would have waited a year! :P
I don't care about 3d but the increased contrast of the 2012 line over the 2011 line makes for a satisfying bump in relative PQ.
What to do if you find yourself stuck with no hope of rescue:
Consider yourself lucky that life has been good to you so far. Alternatively, if life hasn't been good to you so far, which given your present circumstances seems to be more likely, consider yourself lucky that it won't be troubling you much longer...
-- Excerpt from the Hitchhiker's Guide to the Galaxy.