I have to go with Riverview - there's room for extra lots and I really like the characters there. One of these days I'm going to give some of those numerous elders Young Again potions to see how they turn out, as well as enough time to complete their LTWs (sure, I could save them to the bin, but I want to be surprised).
Twinbrook is the most stunning visually in terms of landscaping - I suppose "stunning" can be used to describe some of the sims who live there too, depending on the definition.
I'll admit the town probably has the most interesting gameplay - the main reason I prefer Riverview is because it's really difficult to add extra lots to Twinbrook without major hair-pulling.
Sunset Valley is nice too, particularly the beach area, and I play there when I want a change in scenery. I also think it's a little easier to find seeds and plants here than Riverview.
Bridgeport is great in theory, but it takes too long to get anywhere. When I do eventually tackle maxing mixology in a casual game, I'll do it here.
Hidden Springs...oy. There are some great hangouts that I plan to save to the bin and remodel into clubs for other towns, and the scenery is gorgeous, but the layout is maddening & it's very laggy. I feel like I wasted my money on that one.
I don't have Showtime or Pets at the moment so I can't speak to AP or SS, but I have a feeling I'll like Starlight Shores more, mainly for nostalgia reasons as I grew up in LA.
Both Lunar Lakes and Lucky Palms look amazing and I'd love to have both - visually and in terms of lot placement, I think Lucky Palms will win out, but I'm not getting either town for a long while, especially after my mistake of getting Hidden Springs. Barnacle Bay isn't even on the radar since it sounds like if I don't like Hidden Springs very much, I'll hate Barnacle Bay.