You really should be more succinct in your preferences.
This is like asking a Coke vs. Pepsi question without stating if you like Soda, sugar, or cans

You have different mechanics, different races, different additions. I like pet battles and both are flaccid in any repack, so I continue to play retail till someone realizes 40k+ people are walking if the Pet battle system becomes pointless in retail, but ya know VROOM VROOM RAID !! PVP... It's about fun for some people developing and it's about money for others.
So, you should declare what YOU are looking for to see WHICH suits your desires. I dislike the whole kung Fu panda enviroment, but it did bring Pet battles. I dislike the Edge Lord Elf class, but I liked the quest line and graphic changes.
The LEAST popular Expansion appealed to the largest, silent base, WOD, but that seems to be the least worked on. WOD was a solo player's favorite. You can log in retail, go to a garrison, and say Hi, and your chat gets spammed

It was not so for Midnigth housing...blew that 80.00, ah well. At least I got a nice house that I can PSudo-Decorate...