John Vanbiesbrouck and Mike Vernon were two of the more successful goalies of the "pre-Hasek" period (late 1980s/early 1990s). Vernon is probably better known and considered a better goalie by most, mainly because of his 2 Stanley Cups. He even gets a lot of Hall of Fame talk because he is remembered for those championship runs. But this comparison is actually a completely mismatch in favour of John Vanbiesbrouck.
Between the ages of 24 and 34, John Vanbiesbrouck had a better save percentage than Mike Vernon in 10 out of 11 seasons. This was despite playing on a worse team probably every single year in the span.
Vanbiesbrouck won the 1985-86 Vezina, and he had a dominating season in 1993-94 (.924 save percentage compared to a league average of .895) that was Vezina-worthy but unfortunately coincided with the emergence of Dominik Hasek. In his career, Vanbiesbrouck collected a total of 61 Vezina votes and finished in the top 6 seven times. Mike Vernon only finished in the top 6 in Vezina voting three times in his entire career, peaking at 2nd in 1988-89, and was voted for just 32 times.
Because of the strength of his teams, Mike Vernon played in nearly twice as many playoff games over his career, 138 to Beezer's 71. He won a lot more of them as well. However, the two goalies had identical playoff GAAs (2.68), and Vanbiesbrouck had a much better playoff save percentage (.915 to Vernon's .896). Vernon faced an average of just 25.8 shots per game in his playoff career, while Vanbiesbrouck faced 31.4. Mike Vernon won a Conn Smythe Trophy, but Vanbiesbrouck's goaltending in the Florida Panthers' 1996 Cup Final run surpasses anything Vernon did in his playoff career.
Mike Vernon's biggest advantage throughout his career was that he faced very few shots per game (26.9 regular season, 25.8 playoffs). Considering how much of that came in the 1980s, he really did benefit from exceptionally strong team defence in front of him. I don't recall Vernon as being an accomplished puckhandler or having exceptional rebound control or any other quality that could have had a major impact on those totals. It seems to be the case that he just played on some great defensive teams, which meant there were a lot of winning efforts despite Vernon's shortcomings in goal.
Mike Vernon played most of his career on great teams and had a lot of team success, but he really was a very average goalie. John Vanbiesbrouck was a very good goalie who played on average teams.