Miller has the best chance of getting lots of K's, but he also faces a very tough Boston offense and might not necessarily get the win. Hudson faces a weak, Vlad-less Expos offense and should be able to get the win if Foulke doesn't blow a save on him again but may not get the K's. Padilla really hasn't been getting that many K's even when he's on this year so I'd consider benching him to preserve ERA and WHIP.
How far ahead are you in ERA and WHIP? If you are far enough ahead to take a possible 5 earned runs in 6 innings from Miller and still win those categories, I would start both Miller and Hudson. If the ERA and WHIP are really close, I would just start Hudson and hope for the win and maybe enough K's.