Fish,
I agree, the base on ball factor (or more precisely - the walk to strikeout ratio) is the much more important stat to look at when comparing umps. And you absolutely MUST take a large sample (several years of games) to make a legitimate evaluation. I have spent countless hours acquiring stats on every ump in MLB since 1997. I have them ranked in order - using data on over/under record, strikeout/walk ratio, and ball/stike ratio. I've weighted the more recent year's games higher, since any umpire can change his spots. I have also ranked the umpires for their "homer" tendancies (home/away record in games where they are behind the plate). Interestly, Fish, the ump that you mention as a great "under" ump (Montague), is also one of the alltime best "road" umps (take the road team when he is behind the plate), too. Won for me today again, btw. Incidentally, I have done the same analysis for NBA refs, also, if anyone's interested.