Comparing MacBook keyboards
None, to be frank. They all feel approximately the same in my opinion - the MacBook white 2010 has a lighter feel than the Pro or Air which to my senses are pretty much the same. 

Both the current models and the now out of production white macbook have the same keyboard, to all intents and purposes, apart from the air and pro have a backlit keyboard which possibly leads to a heavier key press - although that might just be because my white machine is older and slightly more worn.