Why You Shouldn't Trade for Arroyo

I notice when people speak about adding a starting pitcher they look to the possibility of trading for Bronson Arroyo. So, I wonder to myself: what exactly does Bronson Arroyo give you that someone like Jon Garland doesn't? For one, you have to trade for Arroyo, whom I'm not even sure the Reds view as a salary dump, and you'll have to pay at least $13M (I'm including his 2011 buyout money, and he can still earn an extra $2M based on IP in 2010 which could push the total to $15M). Garland can probably be had on a 1 year deal for ~$7M.

Lets take a looking at their FIP, xFIP, and WAR from this past season:
2009 FIP:
Garland - 4.48
Arroyo - 4.78

2009 xFIP:
Garland - 4.63
Arroyo - 4.56

2009 WAR:
Garland - 2.4
Arroyo - 1.8

Now, if your argument is "well Arroyo has a stronger history of success!" or something of that nature, then I will say there is no question Arroyo circa 2004-2007 was very good. In that stretch his average WAR was ~3.5, but its not like Garland was that much worse; pitching in the AL for all 4 of those seasons, he averaged a WAR of ~3.3 over that same time frame. What about the most recent years, 2008 and 2009? Well, the same goes for the last 2 seasons, in terms of the equality:

Arroyo's WAR in 2008: 2.4
Arroyo's WAR in 2009: 1.8
Average WAR over past 2 seasons: 2.1

Garland's WAR in 2008: 1.9
Garland's WAR in 2009: 2.4
Average WAR over past 2 seasons: 2.2

I know Garland can be more hittable, his batting average against in 2009 was .25 points higher compared to Arroyo's, but its not like hes getting 'lucky' living off of some high LOB%; in fact, his LOB% has been below average the past few seasons while Arroyo's has been above average 3 out of the past 4 seasons.  

Another thing worth mentioning is the defenses that both of these pitchers pitched in front of last year. Jarrod Washburn pitched to a 2.64 ERA with the Mariners last year; is it any coincidence that the Mariners were the best defensive team in baseball?

Arroyo, CIN, team UZR: 52.6, ranked 3rd best in baseball.
Garland, ARZ, team UZR: 21.6, ranked 9th best in baseball.

The defense analysis is really for the non-sabermetric people who only look at ERA (and dare I say, wins-loss records). Arroyo had a 3.84 ERA, Garland had a 4.01 ERA; do you think the difference in LOB% and the stronger defense Arroyo pitched in front of has anything to do with it? I certainly believe it does, though the ERA differential isn't really much anyway.

I'm not trying to discourage Arroyo in this article or anything of that sort, I think hes a very quality starting pitcher. But why go out and trade for him and pay him $15M [in all likelihood], when you can just sign Jon Garland for about half that price for likely 1 year and get essentially the same kind of production? As a Mets fan, while I do prefer to go with a higher upside starter than Jon Garland, I can only pray Omar Minaya doesn't fall into the Arroyo-love trap.