I like Sunset Valley the most. I've tried lots of downloaded worlds but there was something about each that I just plain couldn't stand. But Sunset Valley only has a few things about it I don't like, so I'm changing those things.
-Turned the hill at the cape into a small, tree-filled area for fancy cliffside houses
-Turned the hill with the mansions into a larger, sub-division-style area
-Added an extra cliff of homes near the beach and behind the town center
-Added an extra "block" where the warehouse was, to allow for a more closed-together block-style feel, that you can't really get with the original sunset valley.
-Added a road near the military base which leads to the roads around the airport, leading off to an area where the warehouse will be instead. MUCH more secluded.
-Removed the stupid terrain rocks around the lake up in the hills, because said rocks prevent you from really putting anything else there ever.
-Added two new houses on the secluded beach
Look forward to it when I eventually maybe finish it. I'm not planning to keep the lot sizes the same, but the town center will probably be identical.