I'll disagree with the replies so far above.
I'm a match-up guy.

Rask & Elliott.
St.Louis is playing the best defense in the league, BY FAR.

Imagine if Brian Elliott was the only goaltender for St.Louis.
Imagine that Brian Elliott played only in a two-team league: St.Louis & Columbus.
Imagine Henrik Lundqvist played only in a two-team league: NYR & Pittsburgh.

Which goalie would have better stats?
Lundqvist playing 82 games vs. Pittsburgh
or
Elliott playing 82 games vs. Columbus

We are looking at JUST one game.
There's no "Lundqvist's other stats against other teams" involved here... just NYR vs. Pittsburgh.
There's no "Elliott's other stats against other teams" involved here... just St.Louis vs Columbus.

With day-to-day goalie sit-start decisions, you go match-ups.
Always.