I would not buy one of those HD sized units for bike building. They are mostly cutitng torches for steel fabrication. For beginers in particular there is a lot of time moving a torch around to get a well brazed frame. The heavy units are vastly overweight for the work involved. Paternek estimates the bottom bracket is an hours work for the Newby. It's delicate and involves precise placement of the flame, off the work and between orther tubes and fixtures. You just won't have the control. Sure try it if you want a big cutting torch.
Also check out your local gas supplier. Mine charges basically the same price regardless of the size of the bottles. So you are going to get ripped for the amount of gas that a HD compact unit accepts. You want standard size bottles they aren't too big anyway.