I have used both speedplay x5's and look keo's.
Right now I Like the Keo's better.
I learned on the X5's and grew tired of the unlimited float, and there was always something that felt unstable about the speedplays. The Koe's feel more solid under my feet, and I think that is worth a slightly more difficult clip in.
If you want to try more float I would first try the red keo cleats. If you just want to try something new, go for it, and sell the pedals you like the least on eBay.