I'm calling bs on those charts. Megahalems 2c difference vs H50. I've seen some members on here say that they've used both and there was a much bigger difference than that. You've got to take these review sites with a grain of salt. Where do you think they get the money to stay in business? The only site I believe to be 100% accurate is anandtech.
People here are enthusiasts. It's highly likely they are running their CPUs at higher voltages and higher frequencies than the reviewer sites.
Let me put it this way. At 6.5 watts, the stock intel cpu cooler would show identical performance to both the H50 and megahalems. At 65 watts the difference would be a few degrees. At 130 watts that few degree difference turns into 50 degrees. And at 260 watts the difference is practically infinity -- the stock sink continues to build up heat until something melts.
I know at least one person running a C0 920 at 4.2 ghz, at something like 1.45 volts (on water). That kind of OC would show a drastic difference between coolers, while my 3.8 ghz 1.1v overclock on a 920 would be hard pressed to show a huge difference between a 212+ and the Noctua. Not a big difference in performance on the two CPUs (call it 10% or less), but easily a 100 watt difference between the two.
The megahalem and equivalent have been shown capable of dumping 180 watts of heat without too much trouble. Smaller coolers are going to have a smaller capacity, and once exceeded build up heat much faster.