There is only one SAGA ruleset - the latest errata brings the original 4 Dark Ages supplements fully in line with C&C.
The Revenants are quite a powerful faction, but cannot be used in tournament play. They obviously have a very different feel to the other factions, and are fun to play. The sculpts are quite nice, and out of the 51 models in the box set you get 24 actual Revenant variants, along with the Necromancer and the 2 Grave Pits. So lots of variety. But if you play them a lot you might want another 12 Revenant models, I have decided.
The rules have a few omissions and grey areas, which will hopefully be addressed in an errata sometime soon.
cheers
CW