The main difference between the two products posted above is that one requires a ceiling box to be installed and then the light to be installed into it. The other product just snaps in with nothing else required.
Depending on your ceiling joist situation and where you intend to mount the lights, the snap in product can be put anywhere in the ceiling while the other one might be limited to being next to a joist. This could be a big difference...or no difference at all....just depends on your particular set up.
CD