My pro-Kari Lehtonen post resulted in a bit of a discussion about shot prevention. One interesting fact that came to light was that Lehtonen faced far more shots on the penalty kill than his backups did. I decided to look around the league to see if this result was consistent.
It turns out that that did appear to be the case for the 2007-08 season. Behind the Net gives breakdowns of shots against per 60 minutes at 5 on 5, 4 on 5, and 5 on 4 situations. At 5 on 5, there was little difference between starters and backups (starters faced 26.1 shots per 60, backups 25.9). While at 4 on 5, however, the starters faced 41.6 shots per 60 compared to 40.4 for the backups.
Another interesting result was that the backups' teams actually averaged more shots for per 60 minutes (26.0 compared to 25.6 for the starting goalies).
Just to be clear, there was a wide degree of variability across the teams, and the numbers above are averages. It certainly wasn't the case that every starter faced more shots on the PK than their backups did. Also, my definition of the starter was simply the guy with the most minutes, so there were some teams in a platoon situation that had a "backup" who was either as good as or better than the starting goalie.
I ran the numbers again for just teams that had what I determined to be a clear #1 starter who played the majority of the games at a high level, and compared their numbers again to the backups. The penalty kill gap remained (41.8 to 40.6), the good goalies again faced slightly more shots against at 5 on 5 (26.5 to 26.2), and the shots for totals were very close (25.5 to 25.6).
I did a different filter and looked at just goalies who played at least 65 games. Strength of schedule would be expected to come into play here, since some of the backups played very few games which were likely against weaker than average teams. However, the heavy workload goalies had both better "shot support" 26.2 to 25.7 and faced fewer shots 5 on 5 (25.3 to 25.7). The PK results were again similar (40.9 for starters, 38.6 for backups).
I checked the 2006-07 data, and the starters did again face more shots while down a man, although it was much closer (46.9 to 46.7). At 5 on 5, the shots were virtually identical (29.1 for starters, 29.2 for backups).
We need to look at a few more seasons to be sure, but it looks possible that better goalies face more shots when on the penalty kill. If so, I am not sure if this would be because of a difference in penalty killing tactics or simply that the other team figures they need to shoot more often against a better goalie. Also, with respect to the starters vs. backups shot totals debate, I think the evidence tends to suggest that in general there is no significant difference between #1 and #2 goalies in terms of shots against per game.