logicaly it would have an impact.
So Davos is at 1500 m.
Geneva, the lowest city is at 375 m.
So you would have a 1125 m difference !
(the very good exemple of NHL team playing in Denver (1600 m) is with many teams playing at 0 (see level) ... so the difference would be bigger)
++
My personal experience of having been in high altitudes ... the oxygen/height relationship is not linear.
i went to 6000 m in Nepal, i must say that the 4500-6000 difference was deadly (the slope was deadly too !) ... while the 1400 m (Kathmandu) - 3500 m was almost a non-factor !
(it is true that it took around 10 days to get to the 3500 m.) do blood cells adjust in this period ?? i am not a doctor. It may be a bit short!
effort wise ... walking with a 10 kg back pack (mine and my girl ;-) ) was ok ! not an extreme thing neither.
++
It is also true that Davos won so far 30 titles (since 1909), the most titled team !!
Yet it doesn't have the greatest budget ! (that should be Bern : 13 titles, 500 m)
Arosa, 1700 m, small budget, won 9 titles. ... Times were different ! are we comparing apples to apples ?
++
I am convinced that you have a point ! that in the long run, it makes a difference. But it wouldn't be striking to the point that at the end of every game, Davos' players are super fit and the others are gazed ! Teams don't speak about making different shifts to compensate for it !
Or that some teams size this element and make an affair out of it.
this definitely not. But statistics (30 titles) gives you right. (i guess) ...
Therefore : Yes it is a factor, with, intuitively, a significant impact over years.
Let's see if someone out there feels a wish to plot a statistical test taking into account budget and height + whatever variable seem appropriate !
but 30 titles out of +/- 100 championships sounds above average ... for sure.
http://en.wikipedia.org/wiki/National_League_A
PS : don't talk too much about it ... let Arno del Curto (Davos' trainer since 1996) enjoy his aura of great head coach ! (which he is ;-) )