Personally I liked TBC more.
I felt like Wotlk was the beginning of the worst.
Achievements, heirlooms, different raid content, gearscore, dungeon finder etc.
Also I didn't like half the patches in wotlk.
Phase 1 raids were boring and totc was also boring.
Ulduar and ICC hard carries wotlk
ulduar is one of the best raids ever released imo.