I've had both Look and Speedplay. I prefer the speedplay pedals considerably - it's easier to adjust the cleats and to replace cleats and duplicate the position. Also speedplay has the most options for accommodating Q factor.

Friction Facts rates speedplay (0.160W) as more efficient than Look (0.230W) and then Shimano Ultegra (I'd presume DA is about the same) (0.360) in that order.

Anyhow, for entry, I don't see a tremendous difference between Look/Shimano and Speedplay. I'd rate Speedplay as slightly better for entry. However, the cleat adjustably is much better and the float is really a big deal to me. The primary reason I went to them is to fix a Q factor problem I have that really alleviated a lot of foot pain.

Keep On Kovers are fantastic. Highly recommended.

J.