I own both X and 8+ and switched back and forth every other week or so. Can not do it any longer as the two phones operate so differently with different interfaces. Decided to get rid of one.
The 8+ is the winner and the X will go on Craig's list this weekend. It is a great phone but the keyboard is most important to me and the 8+ wins hands down!
Just my .02 cents worth, but try swappa.com, never had any issues with them. They investigate the ESN to ensure the phone isn't black listed. I use them exclusively and find they're better than the risks involved with CL. Just my opinion.