I haven't really had a chance to explore everything yet but I think I like Club Pop the most so far. We'll see! I just got a V6 (I know, took me forever, right?) and my Tama-Go is on the way. Discoveries are bound to be made!
Personally, I like TamaTown as a whole. However, I find Swirly Sweet City the most enjoyable. It's a cute little town, and it's also home to the TamaTown Pet Shop! The games there are easy and fun and you can redeem your Gotchi Figures bonuses there too. Overall, it's a great town.
Really, the whole place is called TamaTown - Tamagotchi Music City is just the original part with Gotchi Records, Club Pop, ect. That's how it is in my opinion, anyway.