Ah. ^^; Well, in my case, at least, the Savage Species Imp progression is actually significantly different from the MM 3.5 Imp. I'd lose out on +2 Natural Armor, Survival as a racial skill and +4 Charisma, and in exchange I'd get Regeneration instead of Fast Healing and the ability to choose from a much wider variety of forms for my Alternate Form ability.
To be honest, if I could combine the two, I think I could make a much more interesting character, especially with that increased Alternate Form list. The Regeneration would be great for survivability, but being able to disguise myself as a Coure Eladrin, or a Petal, or maybe even an Aasimar or Tiefling, instead of the standard Raven, Rat, Spider or Boar choices would be much more fun.