It's all about what you want to do with your bike FC. If your going to huck yourself off 15' drops and 20' doubles like speedy suggests, then flat pedals are the only way to go. If you just want to pedal around the neighborhood for fun, or go to the coffee shop then flats are probably going to be fine. If you want to learn to pedal and really work on fitness and strength building, then skip the cages and move directly to the clipless pedals and shoes. Climbing is infinitely better with clipless.
Cages do effect knees, as KX mentioned and also build bad habits that are hard to break when moving over to clipless. In my experience, people with no "cage" experience learn clipless faster than those with "cage" experience.
Cages do effect knees, as KX mentioned and also build bad habits that are hard to break when moving over to clipless. In my experience, people with no "cage" experience learn clipless faster than those with "cage" experience.