I wish I could help, but I've never done 4H so I'm not sure what would be better. For an APA show, I'd want my birds to be older.
There's never a guarantee of show quality, no matter where you buy the chicks. Even if you bought from an APA Master Breeder whose birds had won grand champion at shows and were the parents of the chicks you bought, there'd still be no guarantee.
There's something called the "Ten Percent Rule". In the words of Rip Stalvey, an APA judge, for every 10 birds produced, only 1 is worth keeping. For every 100 birds, 10 will be good breeding stock. For every 1,000 birds, Stalvey says that 100 will be decent, and 1 will be an 'absolute knock-out bird'.
Hatcheries sell every single chick they hatch, so all the ones that aren't decent are going out too, and it's impossible to make sure you're getting the ten chicks out of 100 that will be decent and not the 90 that won't.
But if everyone in your 4H chapter is getting hatchery stock, then since you are only competing against other hatchery stock, it doesn't matter so much. I just wanted to explain what I meant when I said show quality before and why I said you're very unlikely to get a competitive show quality bird from a hatchery.
Those pictures you posted are indeed d'uccles, but since I personally don't breed them and know the breed standard, I couldn't say if they would be competitive at an APA/ABA sanctioned show. I've never done 4H either so I can't say if they'll be competitive in that type of show either, sorry!