The simple fact is that the West Indies from 1974/5 until 1991 expected Viv to get the bulk of their runs. This in turn meant that Viv for the most part had to curb his natural game. Therefore he could not be as free-swinging as Cairns has had the ability to be.
Of course this ends up reflecting his "poor ratio's" as opposed to Cairns, this can only be expected.
Look throughout modern cricket history, maybe even pre-war, at all the No.3's and No.4's, or that were their countries best batter. I mean the likes of Bradman, Crowe, Miandad, Gooch, Tendulkar, Flower, Hammond, Chappell, Sobers, Gavaskar, G.Pollock... the list goes on.
All these batsman had the ability to hit sixes (well maybe not so much Gavaskar, although I did see him go berserk once), but their requirement was to go out and accumulate runs, and alot of them, cause for the most part if they failed their team would lose the Test Match. Viv's amount of sixes, compared to these other primary 'run-getters' is great.
Cairns however is in a breed of aggressive middle-order batsman, who don't have this responsibility of accumulating alot of runs, therefore is more free to take the long handle approach to his batting, I'd expect him to hit more as a result. Probably most of the batters that are in this similar position to Cairns would have better "ratio's" than Viv.
Although '6 hitting' is quite specific, I see this thread as more than just '6 hitting' it's also about "dismantling attacks" when they have the freedom to '6 hit'.
This is where the argument turns a little, as the likes of Cairns, Klusener, L.Cairns, Holding, whilst being able to launch one over the ropes, were not as able to sustain this approach as long as a Viv or Sobers, as it was only a matter of time before the bowler got the above four.
I don't see it happening today, but it was a 'cricketing EVENT', a privilege, when the likes of Sobers, or Viv came anywhere close to play, and people travelled to go see it, why??? Cause people knew, just in case, on that day, they felt like it. That is the ONE THING Cairns doesn't have in this equation.
To me, that shows more to me in what the general cricketing public thinks of what the batter is capable of, than 'ratios'