I think my love for Oasis Springs just comes from how much I enjoyed Strangetown from TS2! I love the desert atmospheres in both games. If it were open world, I might like San Myshuno the best, or at least a close second, because that would add so much to the city feel. Then again, Seasons has changed my perspective on the worlds, and has allowed me to appreciate places like Windenburg that I was pretty indifferent about prior to Seasons.
Del Sol Valley is interesting, but a little lackluster--disappointing in ways that make it seem like nothing more than a copy of the other worlds. Newcrest and Magnolia Promenade are just bizarre.