Cycling UK Forum

Hi all,
I'm new to all this cycling lark and all being well should be picking up my Giant Defy 2 next week. I am looking for some clipless pedals to put on. I think I've narrowed it down to a choice of either Shimano R540 or Shimano 105's. What are people opinions of these pedal, I am on a budget so favouring the R540's but if there was a big advantage could probably run to the 105's
Cheers