Blaziken: Has higher stats in Attack and Special Attack, but has 1 base point lower in both Defense and Special Defense than Infernape. However, it is slower than Infernape, but Speed Boost can take care of that. Has a great ability in the Dream World, and has access to a pretty diverse movepool.
Infernape: Has lower stats in Attack and Special Attack, but has 1 base point higher in both Defense and Special Defense than Blaziken. Faster than Blaziken but Blaziken can easily outspeed Infernape using Speed Boost. Infernape has Priority with Mach Punch, and can learn a few moves that compliment its Dream World ability Iron Fist.
Overall, I think Blaziken is better than Infernape.