Out of sheer boredom (at work) and jealousy (you got Matsu, we didn't), I decided to look up the stats of these two while they were in Japan and came up with a couple of very interesting lines.
Japanese Careers (Nomo 5 years, 139 Games. Mastuzaka 8 years, 204 Games)
Nomo - 78-46, 3.19 ERA, 1204 K
Mastsuzaka - 108-60, 3.00 ERA, 1355 K
These are very basic numbers obviously and don't have stuff like WHIP or BB. Nomo had a .629 winning percentage, Matsu had a .642 winning percentage. Nomo got a decision in 89% of his games (I don't know if they were all starts or not). Matsu got a decision in 82% of his starts (again, I don't know if they were all starts).
If anyone has a better site than http://www.japaneseballplayers.com, I'd be more than happy to see a more detailed comparison.