I was going to say this.
Over the same time span Oswalt has averaged 177 IP. Jackson has averaged 4 more starts per year with an extra 30 IP, with a slightly higher winning percentage, while having a .50 higher ERA. H/9 HR/9 BB/9 SO/9 SO/BB are pretty close between them, but Oswalt gave up pretty much one whole less hit per 9. All this Jackson did with a majority of games being in the AL while it was all NL for Oswalt.
Yeah, I'd take Jackson