The Keo Sprint is less expensive than the Keo Carbon, but it gets there with just minimal changes.
Instead of using a total of three bearings per pedal, the Sprint is built with one outboard cartridge bearing and one inboard needle bearing per pedal.
The axle assembly is marginally heavier than what you get on the Keo Carbon, but it sacrifices no quality at all -- its the same assembly as you get on the ever-popular Look 3.1 and 5.1 pedals.
The Polyamide pedal body is a composite, not alloy, and its representative of the fact that starting in 2006 Look have manufactured pedals with composite bodies only.
The cleats and internal spring mechanism are identical to what you get on the Keo Carbon.