Trimmed/pulled manes are the curse of the western halter horse.
As has been said, if you want to be competitive, you pretty much have to pull and band it. If you're showing under English tack, pull and braid. That being said, running braids have put me in the ribbons in halter classes, but I usually just do smaller shows. OP, what breed is your weanling? That can have a lot of bearing on what is permissible to do to his mane in competition. Sometimes weanlings aren't flattered by braiding/banding, and are shown to the best advantage with a simple trim to even things up.
honestly, if your going to do a competitve show, CUT THE MANE! you have to. halter is mostly judges on conformation, and if the judge cantsee his neck, whats hee gonna do?
This is an argument that I hear all too often. If the mane is properly combed and falls on one side, what's to hinder the judge from making his/her assessment from the non-mane side? I've never seen a horse asymmetrical enough that correctly groomed natural-length mane hides anything that can't be seen from the other side. Shoot, even if the horse was conditioned that unevenly, the shoulders, haunches, etc. would show the same deficiency, nowhere near the mane. Additionally, I haven't been in a lot of halter classes that the judge didn't brush even pulled manes back to better see and feel the neck.
I'm genuinely curious, as this "visibility" argument is the one that I always hear for the pulled look. Personally, my guys spend too much time outside fighting flies to have any less protection than nature offers.
Then again, I don't do western G&S or halter with mine.