I'm a fairly new rider looking to get my first pair of clipless pedals. I've ridden mtn bikes for years with clipless pedals but don't have any experience with road clipless pedals. I have decided on purchasing the spd-sl style pedals but am looking for advice on pedal choice. I am trying to decide between the pd-r550 and the pd-5700(the 105 line). It looks like the only real difference between the two pedals is the weight. Are there any other differences I need to know about? Thanks for the advice!