In my opinion the bar passage rate should be the MAIN issue.
Maybe if you're deciding between two law schools that have 75% and 85% bar passage rates. This wouldn't be a good way to distinguish between the top schools though, because it would suggest changes in overall quality that were far greater than they actually were, since the percentage fluctuates from year to year by a decent number of percentage points just due to random chance.
Also at the top law schools, very little of the curriculum is devoted to bar passage. They assume you'll just learn most of that during the month or two before the bar.