I'll just tell everyone what I know about bitless options :P
The nose of the horse is just as sensetive as the mouth.Tho, some bitless options are just soft leather, and thus might be ''nicer'' than a metal bit. These happens to be the ones that has the least ability to communicate with the horse in dessage; such as leather sidepull or ''bitless bridle''.
But it all lies in the hand.
First out; riding cavessons. Thy have three rings and a nosepart that's either a metalbar or a chain. Great for young horses as you can lead them with the middle ring (or work them on the lunge or in hand) and at the same time have reins for the rider in the side-rings.
The effect is the same as a regular snaffle.
(not a good shot, but he has a riding caveson) http://www.elftown.com/stuff/nacke.jpg
Muserolas/serretas is a metal bar with two rings; you screw it onto the noseband of your bridle (metal bar under the leather, and the rings on top). Same effect as a regular snaffle, and can be used together with a curb bit; good option if you don't want to stuff two bits in the horses mouth.
Some serretas has ''spikes'' on the underside, not very nice and you won't get a horse ''seeking the bit'' with that model. I also recommend short rings.
Sidepull; the softer versions isn't too precise, the harder/stiffer ones should work like the riding cavesson.
Hakamores; the ones with a chain in them is really harsh. The softer ones still work like a curb bit; they pull on the nose to tuck it in, under the chin to enforce the nosetuck, and on the neck. They're stronger than your hand, but is an option if your horse is ready for the curb.
Bosal; as far as I know they are very sharp, and more difficult to master. You can't pull the rein sideways like with a normal bit/bitless.
''bitless bridle'' this just confuses me.. the rein-aids squeses the horses head together in differet ways. Maybe it works, I don't really know..
Rope halters; are harsher than they seem and not very precise. You need to ride a lot with the seat and mainly have the halter as an ''emergency break'' to have at hand if necessary if you want a god result from it.
If you want to do any work with the horse, I'd say that you should use the cavesson or muserola as a first try. You can give correct and precise aids with them. But of course remember; they're not nice just because they're not in the mouth, so be careful with the reins no matter ifit's a bit or bitless.