MoP is better to me just because they gave us more to do, and Pandaria is bar none way cooler than the crappy Cata zones. Vashir was disgusting to everyone except for a few people. Hyjal was okay. Deepholme could have been so much more. In lore it was designed as basically being a giant cavern in the earth. There was no sky to see period. Instead they decide to say screw the lore and gave us a giant crater. Uldum I'll say was pretty awesome. Twilight Highlands was bleh. No one really got to do it anyways. There was no point at 85 in doing it or going there really, and you'd be 85 before you even got there half the time so you didn't even level up there.
Also the Cata entry raids were indeed amazing. In my opinion that was Blizzard's best tier at that point since Ulduar. It was brutally difficult for many people which most of us were happy about because we complained at how easy they made raids and heroics in WotLk. 5 man heroics in Cata were also great at launch for that matter. However I have a negative emotion regarding Cata heroics because Blizzard caved and nerfed the hell out of them.
And Dragon Soul indeed is one reason why many view Cata as a terrible expansion. It was pretty rough in WotLK having only ICC for a year, but Dragon Soul was even worse. At least ICC was new with a couple new boss models for example, and we were fighting Arthas. Dragon Soul was not even in a new dungeon enviroment, and seriously almost every single boss model was something old and outdated. I was shocked when i saw two of the DS boss models were simply a Tauren Male and an Orc Female...
And the Deathwing fight was a MAJOR disappointement. We had just had an amazing end fight with Firelands and Ragnaros too. Then we do Dragon Soul and see what a terrible fight Deathwing is. Especially the Madness encounter. We don't even fight Deathwing, we just see his giant claws.. Also Dragon Soul was only 8 boss encounters which was very very sad.
Cata also failed on the promise of giving us Path of the Titans. And the re-doing of the talent system in Cata was all but pointless.
So yeah so far I'd say MoP is a grand slam of an expansion compared to Cataclysm. In fact overall I'd rate Cata as the worst expansion we have ever had. With the best being Burning Crusade followed by MoP then ICC.