These are what I've learnt to start horses with.
Tho I personally prefer a riding cavesson or an unjointed snaffle :P
The important thing is that it doesn't have shanks and that the horse likes it. With trhe single jointed one, make sure not to strap the noseband tight at all, it can hit the horses palate and then it's rather cruel to keep the horse from opening the mouth to get away from it.
I don't think you can show in unleaded snaffles.. not sure.