There are different needs for each team. I have team Im developing to be NC contender. There I have redshirted my worst rookie DL because i could not get better in recruiting. With the redshirt he will be a decent backup, maybe a starter.
Other times I will redshirt my most Important rookies; not necessarily my best. Like a qb or rb since they IMO are most important positions in game. Qb is obvious why. Rb does triple duty of run, receive and block.
But I will always redshirt the 3 I am allowed just to get max growth. Especially at lower levels it's 70% growth and 30% strategy IMO.