Hmm... this one's a toughie for me. It's between Hyrule from ALttP and Termina.
The biggest reason for ALttP's layout being one of my favorites is simply due to a large amount of nostalgia. I have so many memories traversing that piece of land. Not to mention I've explored it enough where I could probably legally say that I know it better than the back of my own hand. Lol
The reason for Termina though is because its different. And by different I mean, it doesn't have the usual things that we've come to expect to find in Hyrule. Sure, there's some similarities here and there since the two overworlds do belong to the same series, but regardless, Termina has more interesting things going on than Hyrule does at times (minus the fact that there is a giant moon floating over it spelling out certain doom for its inhabitants...). It has also some landmarks there that I love to explore when I play the game and I just find its inhabitants and cultures interesting.
Kinda makes me wish we could travel back there one day just to see how the place is doing after Link saved it in MM. Probably won't happen though...
And as far as what area is my favorite it would probably be Clock Town. Just because it has a lot of things going on in it and has a lot of life in it when compared to other parts of the surrounding land.