Fairy tail= Nothing but a fun, easy going story with no complex themes or plot. If you like to have many characters in the show with cool development and usual shonen jump main character that is all about "My fiends give me all the power I need" then go ahead and watch it. Deaths/emotional moments are rare in FT, or at least in my opinion there weren't many.
One piece= Emotional story with insane development for the main character and the strawhats aka his crewmates, adventure is mostly everything here, so expect as much weird shit as you can XD. Anyway main character is trying to be a legend on the sea and as the story goes on,he picks up people from different islands to join his crew. This is definitely recommended, though the pacing may be one of the worst, however events that happens in each arc makes it worth it so don't give up.
Bleach is better than both imo.