Rope halters are a great tool for training horses, as they do not have any metal hardware on them, as do typical nylon halters. The metal is generally the piece that breaks if a horse sets-back on his rope.
Another great use for rope halters is for trail riding. They fit easily under most bridles, tie onto the back of a saddle, or can be "stuffed" into a saddle bag, and used if you need to stop and dismount.
It is important to tie the "poll strap" around the tie loop, instead of over it, back around the poll strap, as a halter that is tied "over" will have to be cut if the knot tightens. A halter that is tied "under" can be loosened, which means you don't have to cut your halter!