So.. Rock&Pop. I have a choice for a birthday present, and Idk which one to choose .?

I'd pick the guitar, it'll pay off more in the long run. U2 put on a great show though, and they say they're trying to keep tix prices for this tour in the $30 range, so I'd go with the guitar for the bday present then get the U2 tickets with your own $$$ if you've got some to spare and if you really wanna go see them.