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.
Always keep your head up, but be careful to keep your nose at a friendly level.
I like this bit a LOT for horses who don't respond well to a snaffle. It has the three piece, has a copper roller to soften the mouth and give extra pressure on the tongue, and has the full cheek to aid in steering. Schneider Saddlery