Is SIERA better than other pitching metrics?

Baseball Prospectus came out with an interesting article today that provides evidence that SIERA is the best indicator for estimating a pitcher's performance.  It's a good read and fairly easy to follow.

http://www.baseballprospectus.com/article.php?articleid=12793

This little section is of particular interest to me because it details just why the author believes SIERA is the best estimator:

My further research over the last year has helped me understand why. The following are the highlights of      this research. The first one listed is the one that we knew already when we published SIERA last year, but it is not the primary reason at all.

1. Ground balls matter more for pitchers who get more walks and fewer strikeouts because they allow more runners to reach first base.
2. Ground-ball pitchers allow fewer hits and fewer extra-base hits on ground balls than non-ground-ball pitchers, and SIERA acknowledges this effect due to its negative coefficient on ground-ball rate squared.
3. Pitchers with higher ground-ball rates (but not too high) allow the highest BABIPs and SIERA picks up on this reversing effect of ground balls on BABIP due to their correlation.
4. Pitchers with higher strikeout rates allow lower BABIPs and lower HR/FB rates, and SIERA picks up on this correlation. This is why the coefficient on strikeout rate in SIERA is so negative--because pitchers with high strikeout rates not only prevent runs by getting outs, but because they also allow fewer hits on balls in play and fewer home runs on fly balls.
5. Pitchers with higher strikeout rates get more ground balls in double-play situations.
6. Pitchers with lower walk rates issue more of their walks strategically, and thus the average damage of a walk from a high walk pitcher is higher, another effect which SIERA picks up.

My educated guess is that reasons 2) and 4) are the primary reasons for SIERA's superior estimation skill. The stark difference between QERA’s RMSE and SIERA’s RMSE in last year’s testing was primarily due to the negative coefficient on ground-ball rate squared in SIERA. When we ran our initial tests on SIERA, the inclusion of a variable for the square of ground-ball rate often did the most to improve estimation. Further, even though pitchers do have some control over BABIP, the amount that they do control is very similar to the amount that SIERA credits them with through BABIP’s correlation with strikeouts and ground-ball rates.

I know there has been a lot of discussion about advanced pitching metrics on this site so I thought this article was relevant.  I know personally I have been a proponent of xFIP though SIERA does seem to be better.  It is good to know though that xFIP has outperformed tERA and FIP for the most part.  So now that we all have to acknowledge that there is yet another advanced metric to be aware of let's take a look at 2010 performance for some player's of interest:

That's a little more palatable than looking at just ERA however we all know our defense has not improved much so I wouldn't surprised to see the ERA's for Ohlendorf and Maholm to be a half to a full run higher than the listed SIERA.  Also, note the ERA for Zach Duke.  I put him on there as well because this stat basically awards a ground ball pitcher for throwing groundballs.  It was interesting to see that Duke and Maholm had the same SIERA in 2010.  Anyway, I have no real conclusion here I just wanted to post as some food for thought.  Enjoy.