Actually ive seen the HD4000 beating HD6550D on most of the game bechmarks.
But, gaming and mining are two diferent things anyway.
Those benchmarks are only because the GPU is not the bottle neck. Some games leverage the CPU more then others, in those titles intel wins in FPS not because its GPU is faster.
also 6550 comes in different flavors (mobile/desktop) the mobile line runs 444mhz, the 3870k desktop starts out around 600 ? when comparing the benchmarks at least make sure you are comparing apples to apples.