All personal preference. I really enjoyed classic 60, and I am also enjoying tbc classic. However, there are some very serious and glaring problems with the game design of tbc. I think the raiding is better in tbc, I think the slowing down of PvP is good in tbc, but I also think PvP/PvE gearing separate is bad. I think resilience as a stat is bad for the game. I think the idea of arenas in a game balanced around large group play is bad because of how impossible it is to balance. I also think the rating system is bad because gear discrepancies between competitive play is just too large of a factor in who wins. Gear should matter little in a hyper competitive ranked game mode. This is why arenas never really took off and became a big thing. And the biggest flaw of all, tbc completely invalidates all of the old world. All of the zones in classic 60 we’re filled with people of all levels even in the end by the time I was in full naxx gear. All that is nul and void with the release of tbc. And then tbc is nul and void with the release of wrath. I think it was really badly designed from this perspective.
That being said, I do enjoy tbc for what it is.