I just did a quick calculation using your scoring system and applied it to last years stats. Manning would have outscored Culpepper 225 to 213 using your system. Consider last year was a typical Manning year (he's had 100 INT's over his 5 year career, so expect another 20 INT's this season, and he's averaged 4100 yds and 28 TD's) and that last year was not Daunte's best stuff.
You can bank on Manning throwing 4000+ yds, 28 TD's, and 20 picks. Now decide what you think C-Pep will do and make your decision off that? If it's me, I'm taking C-Pep, considering they really came on once they got McKinnie back and last year's stats were a sort of "down" year for him. Gotta take some risks to win in fantasy. You'll never win if you try to rest with guys hoping they all repeat stats the year before. Never happens. It's all about taking a few solid guys and trying to project what guys will break out or be fantasy factors the upcoming year.