unfortunately, there are too many variables to ever be able to conduct real scientific tests/analysis.
And it has been my experience that generally speaking, a villager is a "mutt". That is, who knows what its heritage is, and who cares. 9 out of 10 will be wonderful companions - but there's always the one that will bite you.
The kamis don't like to make villagers, Pala doesn't like to ship them, and Bill didn't like selling them. But we sure like to buy 'em.....
I think if we got to see how they were made in person, we would be equally disgruntled and amazed.
To answer the question.....honestly, I haven't had enough villagers around to do good enough comparisons. I usually take good care of what I've got, but if it rusts, I just clean it off.....guess I should pay more attention.
I've said this before, but bears repeating (apologizing to those who've heard it)
If you use your khukuri, let it "cool off" before you re-sheath it. You build up heat in the blade, which causes the air around it to condense. In the open air, this is fine, because it will evaporate. Inside a sheath, it will sweat - leather is a wonderful insulator - and will rust. This is a fact whether your sheath is leather or kydex, treated or not. (this is why many khukuris have rusted tips)
Then, on top of that, if your sheath is unprotected veg-tanned leather, the acids left over in the leather will add to and quicken the rusting process.
There ya go - sorry I can't be of more help.