Holliday's OPS+ (ballpark independent) the last 4 seasons: 137, 151, 138, 139. He had a bit of a blip in 07, but has otherwise been consistent. The ballpark factors at Oakland and St. Louis (according to Baseball Reference) last year were 99 and 98, meaning both slightly favored pitchers. Citi had a 98, so Holliday's overall numbers from last year are more or less what you should expect if he came here. Bay's OPS+ the last 4 seasons: 138, 94, 134, 134. 2007 was a lost year, but you probably know what to expect from him, which is a bit less that what you should expect from Holliday. He will hit more home runs, perhaps 10 or so more, but Holliday will make up for it with more hits and a higher OBP. And if the cavernous gaps in left field are considered when evaluating offense, they certainly need to be considered when evaluating defense. Fangraphs has Holliday saving 23 runs relative to average over the past four seasons, while Bay cost his team 40 runs in that stretch. The Fielding Bible is more conservative, but it still has Holliday at +10 runs and Bay at -19 over that stretch. Both sites show 2006 as Bay's one positive year and Holliday's one negative year over the last four, so if if anything Holliday has gotten better while Bay has gotten worse. Honestly, I think it's obvious who the better player is, and would make my offers accordingly.