I'm not entirely sure what you think a +/- would be telling you, as teams who pull their goaltender are already losing the game.
I think the only simple and meaningful analysis would be to compare a team's 6-on-5 goals for per minute to their 5-on-5 goals for per minute. If they're more effective 6-on-5, they should be taking the chance.
I think the only simple and meaningful analysis would be to compare a team's 6-on-5 goals for per minute to their 5-on-5 goals for per minute. If they're more effective 6-on-5, they should be taking the chance.