To Loan or not to Loan

Scenario:

Young players that are fairly promising, not sure fire stars or wonderkids but players who have the "potential to be a good player".

My club has excellent training facilities.

They would be loaned into the championship or league 1 as a first team player.

What do you guys do with your promising youngsters when they are 17,18, or 19. Do you send them on loan or do you like to keep them in the reserves so they can get the benefit or the great training facilities. Or do you perhaps send them half a year on loan and stay half a year to train? Should I require that the team they are going to has pretty good training facilities themselves?

Basically it boils down to this. What is better for them...top notch training and coaching, or first team playing team in a lower league?