The front page post provided us with the general statistical information concerning the pitchers scheduled to start for the Phillies and Reds in their NLDS matchup. I thought I'd provide a little more statistical information--namely, how the scheduled starters have performed against their NLDS opponents over their careers.
Pitcher G W-L IP H R ER BB SO ERA WHIP
Halladay 4 1-1 31.2 35 11 10 7 33 2.84 1.326
Volquez 2 2-0 12.1 7 1 1 4 16 0.73 0.892
Oswalt 34 23-3 218.0 194 71 68 56 175 2.81 1.147
Cueto 4 1-2 22.2 22 16 15 7 8 5.96 1.279
Hamels 7 6-0 50.2 28 7 6 18 42 1.07 0.908
Arroyo 8 1-5 39.0 45 29 24 14 28 5.54 1.513
Most of these statistics suffer from the ubiquitous problem of small sample size, with the notable exception of Roy Oswalt, who has pitched the quivalent of an entire Cy Young Award-caliber season against the Reds in his career. Cole Hamels and Bronson Arroyo have both pitched more than a handful of games against their NLDS opponents, with vastly different levels of success. Hamels has been more succesful versus the team against which he made his major league debut than any other opponent, while Arroyo's career ERA and winning percentage versus the Phillies are the worst he has versus any team against which he has started more than five games.
Edinson Volquez's and Johnny Cueto's numbers versus the Phillies are skewed by the extremely small sample size, Volquez to his statistical benefit and Cueto to his detriment--he started the game last season where the Phillies put up 10 first inning runs on their way to a 20-1 victory behind Cole Hamels (about a dozen starts worth of run support for 2010 Cole Hamels).
So what does all this mean? There is almost no statistical significance to the respective numbers for the Game 1 starters. So we'll have to base our determination of who has the edge on the fact that the Phillies are offering the NL's most dominant starting pitcher from 2010 in Roy Halladay versus a guy who made only 12 starts and is little more than a year removed from TJ surgery. (Although to his credit, Volquez's last four starts have been very successful--one of them actually against a decent offensive team.)
With respect to Games 2 and 3, the Phillies clearly have a significant edge, with both Oswalt and Hamels enjoying extraordinary success against the Reds, while Cueto's and Arroyo's numbers versus the Phillies could not be accurately described as anything better than mediocre. (And in fact it's fair to characterize them as poor.)
There isn't really anything here that would come as much of a surprise to anyone, but it's nice to know that there are statistics that back up the conventional wisdom that the Phillies have a substantial edge in the starting pitcher matchups for the NLDS.