I have 3 points to make:
1) the "best bit" completely depends on the horse, particularly the horse's mouth conformation... as well as size - what size of bits are these?
2) I don't like any of them. They're all a single-joint, which pinches the tongue, has crackerjack action, and when pulled on, protrudes upwards into the horse's palate.
3) The bits have different actions, and each horse will like a certain bit.
The first bit is a single-joint full cheek snaffle. This is a bit typically used on younger horses for a number of reasons - firstly, the full cheek arms do not allow the rings to be pulled into the mouth. Secondly, the full cheek arms press against the horse's mouth creating pressure on the opposite side of the face when you use rein pressure the other way, i.e. if you pull on the right rein, the horse's mouth on the right side will be pulled on, as well the full cheek arm on the left side will put pressure on the left side of the horse's mouth.
The second and third bits are Tom Tumbs, but have slightly different shanks. It looks like they are both sweet iron as well. There is not much difference in the purchase, but the shank length is different, I'd say the second is "more severe." These two bits are leverage bits.
The fourth bit is a simple loose ring snaffle. I don't like the single joint, as I stated before. The rings can also pinch the sides of your horse's mouth, so beware of that.