Brady is more valuable. QB is just way too important in the NFL.
The other elite QB's win every single year as well, Peyton Manning, Aaron Rodgers. Pencil them in for division titles and double digit wins and they've played for some idiots as head coaches.
If you put Brady on another team for 15 years, you would feel pretty confident he would make that team a perennial contender for pretty much that entire duration. If you put Belichick on another team, he would be subject to all kinds of variance. He might find a QB in that time period, he might not. He might hit on his draft picks, he might not. He might run good with the health of his players, he might not. There's just a level of sustainability that comes from having a great QB that doesn't come from having a great coach. We've seen this with other teams.
I think Belichick is the best coach of all time and it isn't even close, but the history of sports is littered with great coaches that didn't have the same amount of success without their best horses.
Jims and Joes > Xs and Os