Why Do Vgchartz and Neogaf Hate Each Other So Much?

[mornelithe]

MohammadBadir said:

GAF doesn't think that VGChartz has reliable numbers despite ioi's constant reminders that VGC numbers are all estimations. VGC was banned on GAF because of their "misleading numbers".
Now VGC users hate GAF because of all that :P

Is it really that, or is it more that the estimations are then used to drive argument/superiority threads?  Genuinely curious, I've never gone to Gaf, so I'm in the dark.