Well nobody here agrees with that more than me - I've even had death threats for claiming that El G, like most of his rivals, was likely doped.
Clearly Kipchoge even if dirty, isn't able to go full throttle, but it's arguable that the the 'move to the roads' of so many track distance runners from the EPO era, including Kipchoge (and who knows that benefit he might still be getting if he was doped back then) was in part due to being tested less often on the roads.
I'm not an expert on the ABP, but presumably it depends on being able to test the runner being profiled quite regularly, something hard to do surely for a Kenyan who only competes twice a year.
Now that testing is getting ramped up on the Marathon, and we're already seeing bust, including last week of the half-marathon world record holder, how do we know that these times wont appear as crazy as the track times of the full throttle EPO era? Maybe the improvements in times being made now are wholly down to the shoes as many suggest.
Really it's hard to make a comparison between which is 'most impressive', given that the main factors involved are likely quality of doping testing.