Hard to say. 7D's sensor has high pixel density, so most lenses do not have such high resolution. In other words, each pixel has poorer quality compared with 5D's pixels.
A simpler question to answer is comparing 5D with 5D2: They have the same sensor size, so 21MP is clearly better than 13MP.
A simpler question to answer is comparing 5D with 5D2: They have the same sensor size, so 21MP is clearly better than 13MP.