Voted for Brindleton Bay because it is just so beautifully rustic and sometimes a little gray - it just is very moody and expressive, not to mention interactive as most of the worlds are as well.
I do love Windenburg because of its architecture and feel, I need to play in that world more often honestly.
Finally, my third favorite is Del Sol Valley - which I know is kind of an unpopular opinion in terms of gameplay at least, and I totally get that. It could be MUCH more immersive. But it is based off of my home and I recognize a lot of the inspiration, and so much of it has outstanding accuracy. When you go up to the top of the Pinnacles and look at that crazy view... It gives me a level of appreciation for LA that I don't always allow myself to have because I am one of those grumpy natives.