MTV Multiplayer's Russ Frushtick has studied the two game's Xbox Live Arcade statistics for both side-scrolling, curse-inducing games and declared Super Meat Boy as the more rigorous experience.
He has four metrics of comparison. Such as:
N+: Percent of Total Registered Users Who Have Completed The Final Level (Episode 49) - 2.20%
Super Meat By: Percent of Total Registered Users Who Have Completed The Final Level (7-20X) - 1.04%
Do the laws of mathematics allow me to hereby declare Super Meat Boy as twice as tough as N+?
Which Is Statistically Harder: 'N+' or 'Super Meat Boy'? [MTV Multiplayer blog]