I like number 2. Though with the river being so small, that means there's more ground to put PWP's on. To some people this might sound like heaven, but to me it's a nightmare. After a while, I run out of ideas on how to decorate the town and end up resetting due to feeling like a failure xD
So now I keep that in mind and I went for a town map that is much like number 2 but with a longer river.
#4 has a nice, even land distribution that I really like and the straight river is pretty neat. #2 looks good too, but there's less land on the second area. I can't pick either of them though, because it bugs me that neither has access to the second beach without a wetsuit equpped.
As such, my vote goes to #1. There's a good amount of landmass in both areas and you can walk onto both beaches.
I like number 2 because it's like a small, private housing area. You could put your character(s) and some villagers over there. Everyone has to cross a bridge to go to Re-Tail or the town hall. It seems cozy.
i like both 1 and 2 but i'm leaning towards 2 because of the "island" and the private beach and the position of the buildings means you have a ton of space for PWPs and houses.
i dislike horizontal rivers and waterfalls so 3 and 4 are out.