ooooh crap. short answer..both, if you can. Both are so different, both so good. Stern knocked it out of the park on these titles. Rock solid reliable and they play very well.
Play both and see if you can only have one. I have lotr, never leaving and if i could find spidy it would never leave also so I guess I am no help at all. lol
Great games you will lose nothing on having for a while so enjoy, worry free and buy the nicer example and hole out for the other..