This was the question posed. I don't see anywhere in it where there are more than 2 options given. Archie or Cut. Obviously the players themselves are most responsible for what occurs on the field. The question asks who was most instrumental in the development of these two.
I tend to agree with utfantilidie. As parents, Archie and Olivia instilled a sense of hard work, committment and a never-say-die attitude that, so far, has served them well. Cut does have an EXCELLENT reputation for turning out great QBs (None of which will ever sniff a Super Bowl victory without a talented supporting cast), and I'm sure his mentoring the Mannings has had a positive impact as well.