Just browsing through MLB Trade Rumors' projections of the Elias rankings for free agents, and there's an interesting item in there, though it's better for conversation than anything else: Josh Willingham would currently be a Type A free agent, while Adam Dunn is still projected to miss the Type A cutoff and be a Type B.
Now, Willingham isn't a free agent until next season, but this is interesting for two reasons: First, if Willingham has a solid year next year, he could bring back two picks if the Nationals lose him in free agency - and could be a pricier move for some team wanting to sign him. And second, it sheds some light on the valuation process around baseball - which hurts Dunn in some cases.
According to MLBTR, Elias evaluates first basemen, outfielders and DHs on a set of basic statistics: plate appearances, batting average, on-base percentage, homers and RBI. The only stats where Willingham would fare better than Dunn are batting average and on-base percentage (Dunn's OBP, by the way, ended up at .356 this year, 42 points below last year's mark and his lowest since 2003, as he took a more aggressive approach at the plate and swung at more pitches). But there are fewer outfielders who offer Willingham's level of production than there are first basemen who offer what Dunn brings, and because of that, Willingham is seen as being (a hair) more valuable in the Elias projections.
It's important to note, too, that none of this takes defense into account; both Willingham and Dunn obviously have their warts there, though Dunn's are obviously more well-documented. It's just on offense, and Willingham scores slightly better, as a player whose production is harder to find at his position.
It's a thin margin - Willingham is currently projected as the third-lowest Type A player, while Dunn is the second-highest Type B - and again, Willingham isn't a free agent until after this year. But if the rankings hold up, it paints things in an interesting light for the two veteran cornerstones whose futures with the Nationals are most in doubt.