i've only ever used the beautiful town and night owl ordinances. my favorite and the one i currently have in my town is the beautiful town ordinance though. i love not having to do daily watering and pulling weeds.
I always pick beautiful for reasons almost everyone else has listed, but if I had the patience to keep all my flowers alive and fish out trash, I'd probably say Night Owl is my favorite since most of my Animal Crossing endeavors begin after 11pm
bell boom, because my villagers love it and it really helps with making lots of money- especially when you factor in island bugs being sold at the same time
I'd say the beautiful town just because I always use that one... but it really would be nice to use the bell bloom or the late night ordinance without watering all of my flowers.