I agree a well trained horse should not need a chain. Then again a well trained horse should do well in mild restraint (ie a flat halter). I know they are adjustable but I have seen a lot of them poorly fitted and poorly used. I am not saying they don't have a place. I am saying I see a lot of people call the vet out for vaccines. When we arrive they are chasing the dam horse around with this rope halter trying to catch it. When the owner does catch the horse they don't know how to tie the halter on. Meanwhile the horse, is a total snot. I end up running to run to the truck for the twitch or tranq. We can't chain their nose or lip because you can't fit it. In the space of the appointment I don't have time (or the ego) to "fix" their horses unasked. I just see a lot of poorly behaved horses and their owners using rope halters. As a result, from what I have seen I am not the biggest fan of rope halters. Its not the law its just my opinion.
Heck the farrier has a huge heavy halter. Its actually really cool for snotty horses, its got a metal loop for the noseband. He puts that on the snotty horses and shakes it on the nose. They snap right into line. Its great, it weighs about 15 pounds, but I would not use it on a horse that does not need it.
In the end, rope halters are a polarizing one. I think the original poster should do what she feels works for her and her horse. I don't think you should buy a product because someone else told you its the best thing ever. You should buy a product because you think can help or benefit you and your horse in some way.