Which Clipless pedals?

I'm currently using LOOK Delta on my road bike and I have a spare set of LOOK Keo pedals that I was going to "upgrade" to.

The difference in weight of the pedals is obviously immense. But other than that, is it worth upgrading? Reading around on the internet seems to say Keo's are harder initially to get in and out of, but more secure when out of the saddle.

Any advances on that?

Cheers.

EDIT:

I have switched and here are my initial thoughts:

• Deltas are easier to get into. I think this is probably because they are heavier, especially on the back.
  
• Keos are easier to walk in.
  
• Keos have a "medium" float as opposed to the loads or none of Deltas.
  
• Keos are lighter.
  
• I haven't really noticed that Keos feel more secure etc. but I sort of thing they are. But the Keos have new as opposed to worn cleats and I now have new shoes with carbon soles... so really any opinion on that is fairly worthless.