At the risk of sounding like a Conservative:
He's the walking, talking example that AV would've given us "2nd best" politicians - Who was the most popular with the public, most popular with the party, most popular in the first three rounds, until... AV gives us the miserable, little compromise Miliband.
Again, I'd have to argue - as someone who is opposed to AV - that it wasn't AV's fault that Labour had an awful selection of leaders to choose from. The only reason the David vs Ed contest was competitive was purely down to David's platform to be the continuity candidate, the staunch New Labourite, and as such was far more transfer repellent - despite being the obviously more charismatic and leader-like option - from the majority of Labour members wanting a more left-leaning direction.