proven players are better than picks percentage wise.
The player is already good so that is a 100% hit versus
What is the percentage of 1st round picks that even become starters?
If it wasn't for the salary cap, this is a no brainer. The fact that the NFL has a hard cap does give an argument that the value of a pick that you can get a player for less money makes is a little more balanced.
But it is a fact that all NFL teams are poor at drafting.
too many factors:
1) Injury - Health status is a relative unknown even with physical
2) Ability to adjust to NFL and money
3) Character can be checked but really how much do these teams get to find out
4) How skills will translate at the higher level
5) Ability to absorb the large amount of information for game plans
You can do your homework until the cows come home and not get it right.