I had both drilled very similar, they were two different monsters.  The Invasion was more of a controlled motion down the lanes with a decent backend reaction.  The Mutant Cell went very long for a solid ball and made a hard move off the backend, more angular.  I have since traded my Invasion away and kept the Mutant Cell because it's just a better matchup for me on oilier conditions.  Hope this helps, I know a lot of people that have both and like them.