I've read two good articles recently about how Cliff Lee has had an advantage over Roy Halladay and almost every other AL starter this year -- the quality of the hitters he's faced has been extremely low.

From Batters Box users Magpie and zepelinkm:

Anyway, the overall impact is truly striking - Halladay has pitched against somewhat better offenses (his opponents have averaged 4.81 runs per game, Lee's have averaged 4.58 runs per game.) But Doc has pitched far more often against better teams, not just teams who score more runs, and he's generally been matched up against better starting pitchers. It's not particularly close, especially when it comes to being matched up against the very best teams in the game.

From Joe Sheehan at Baseball Prospectus:

Let me run the data this way, because I think it illustrates the point. The following numbers are the team EqA ranks for each not-in-common opponent, highest to lowest.

Halladay: 3, 4, 4, 4, 9, 9, 9, 11, 11, 14, 14, 14, 14, 17, 18, 18

Lee: 7, 7, 7, 12, 13, 13, 21, 22, 22, 25, 26, 27, 28, 28, 28

I think there's a more direct way to look at the disparity of offenses faced by the two pitchers, however, using BPro's Pitchers' Quality of Batters Faced stats report.  The average OPS of hitters faced by Roy Halladay (weighting their OPS's by number of plate appearances against him) is .766.  Cliff Lee's hitters are at .731.  That's a .035 point difference in OPS, which over approximately 800 batters faced is worth five runs -- a .050 point difference in OPS over 600 PAs is approximately five runs, given the same OBP/SLG profile.

Okay, so how much does five runs matter?  Well, it's about half a win for a team.  But on the individual scale, over Cliff Lee's 200 innings, five extra runs would bump his ERA up from 2.28 to 2.51.  Or removing five runs from Halladay's 2.64 ERA over 220 innings would cut his ERA down to 2.43. In other words, Lee's advantage over Halladay in ERA nearly disappears.

Finally, and without much commentary, here's how the two pitchers compare in a number of non-traditional metrics (before applying the above adjustment, naturally):

Halladay's innings advantage counters Lee's FIP advantage and they split the xFIP and tRA battles.  One of these guys won't win the Cy Young award, but was just as good as the one who will win it.  Can the BBWAA hand out two awards this year and forget about third place?

FIP-RAR and FIP are from Justin's stats, xFIP is from The Hardball Times, and tRA is from Stat Corner.