Ideally, you would want to have both the best gear and a high skill level.
You won't be successful without both, at least in the highest levels of play.

If you take someone with the highest rating (arena/rated BG's) and give them a fresh to 80/85 team, and put them against a team that is halfway towards the best gearing, I'm not sure that they'll even stand a chance. But if they're skilled/good, they'll beat the better teams with less gear then I'd need to beat the better teams.