KHS folder (18" wheels) for short trips. I'll use it mostly for rides of 10 miles or less. It has a rack. I like it because it's compact and very maneuverable. The maneuverability is important because in my neighborhood I use some local short cuts through moderately rough areas with lots of fist-size rocks. It fits every bus bike rack I've ever tried. If the racks are full (not uncommon) I can fold it and take it on the bus.
My backup bike is an Electra Townie with rack and panniers. I use it for longer distances and bigger loads. It's got heavy duty tires & tubes because of all the tire puncturing debris I encounter when I get out of my neighborhood. It'll stand a direct hit on a pothole that would destroy my 18" folder. I bet the Townie would take a total load of five or six hundred pounds. That's the bike I took last year when I spent a week exploring unpaved back roads in two East Texas counties. But it's a very heavy bike and it doesn't fit the bike rack on some of the city buses. My avatar is a pic of me on the Townie riding about 15 mph straight at my son who was working the camera, he jumped out of the way at the last instant, we were on an overnight tour to the next county.