Why is scrolling on my iPad faster than my Mac?

I own a 2011 MacBook Air (13"/256GB/1.7 i5), and a 3rd generation iPad. Why is scrolling (for example on theverge.com) stuttery on my Air, yet super smooth on my iPad? (which is driving almost 2 million more pixels)

Is it to do with the Intel HD 3000 graphics vs the quad core A5X? Surely the GPU and CPU in the Air is faster. Or is it just a case of scrolling not being optimized on the Air like it is on the iPad?