I dont know. As you said grassinzimsteeth, its almost impossible to compare batters to pitchers in terms of values. You need to compare within a specific group. Heck, its hard to compare a secondbaseman to a leftfielder, let alone a pitcher to a left fielder.
Anyway, with this impossible task looming over me , I chose Pedro simply because of what he means to the town (Manny was just bought, plain and simple, and even though Pedro was too, it seems like it is to a lesser extent). He can be the most dominant pitcher in baseball, and his outings often set the tone of an entire series. He gives us momentum, which really cant be quanitified, but its important nonetheless.