Loose ring without doubt. But I don't like single jointed bits unless they are shaped to avoid the nut cracker action. I feel horses generally go better in loose rings as the bit is harder to get hold of and more mobile in the mouth enabling them to mouth it better.
The eggbutt actually refers to the rings not the mouth piece. I much prefer egg-butt but I think loose ring look much more pleasing to the eye.
The loose-ring snaffle is the norm. This is a simple bit that is simple to make, and works for most horses. One of the down-sides is that the ring slides through the hole at the end of the mouth piece, and could potentially pinch the horse in the lip. Another problem is that there is a space between the ring and the walls of the hole, so the metal parts can rattle some. I personally know a mare that hated all things that clicked and rattled. So for her we had to move on to...
Egg-butt snaffle.
The egg-butt snaffle. In this snaffle the mouth piece is jointed to the rings by a wide tunnel in the butt of the mouth piece. The ring is thinned where it goes through the tunnel, and the mouth piece is rounded and smoothely contoured against the ring angle. There is no room for rattle here, and also no room for a lip to get pinched. The only downer is the price, which is usually higher due to the higher production costs.