Sometimes I walk 2-3 miles a day for a few weeks, then I lose interest and stop. When I walk, I notice it causes some pressure in the ankles, knees and hips. Recently I pulled a 12 speed bike down out of the garage and started using it again after too many years. Last couple of days, I've ridden 4-5 miles on a flat country road. Can't take hills yet. Seems like I get the same basic effect from both as far as legs and lungs and other things, so is one any better than the other?