Phil,
I don't think there's one answer.
I think conditions of the day, hole location and the golfer's play of the day dictate how best to approach these greens.
Ideally, a golfer would prefer to be below the hole, leaving an uphill putt, however, when trouble looms behind the green and the hole is located in the back of the green, leaving an approach short of the hole may be the safer tactic.
In the real world, I think most tend to approach these green aerially, because they can't depend upon turf conditions fronting the green.
All too often, the approach to the green is soft, which defeats play along the ground.
Given the option of a known quality versus an unknown quality, golfers will opt for the aerial approach.
Wind, turf conditions on the green and fronting the green, the juxtaposition of hazards, hole locations,the golfers game and his comfort zone all infuence the decision the golfer must make.