The biggest difference between the two directors is that Chu is a self-professed "fan" of G.I. Joe, while Sommers (reportedly) wasn't. While speaking to Moviefone at the American International Toy Fair, Chu agreed that it wasn't easy taking over a sequel from a non-fan.
It's hard, but I think everybody felt like we wanted to do a sort of re-attitude toward the movie. And that's part of the tradition of G.I. Joe, that it reinvents itself every several years. So it's sort of inline with what had been done, you know, whether it was in the cartoon or if they changed the theme song to another theme song. To me, all of those different transitions are what makes G.I. Joe so great.