Stay at club or loan

Hey guys.
Sorry if this has been posted before, but I was not able to find the other thread (if there were any).
I am playing as a club with very good training, youth training facilities and youth academy. Is it best for my young players to stay at my club or to be sent on loan to a club in a lower league with much worse training facilities? Do they develop more if they get first team football or play at my youth or reserve team? First team football > Top notch training or is it the other way around?

first team football is the most important thing...