The longer handle is considered a safety feature in that your inseam is probably less than 36 inches so if you swing the axe toward the Earth - say, while splitting - and you miss the target, the axe will hit the ground before it hits you. This doesn't address a dozen other likely scenarios and for me a 36 inch handle doesn't have a lot of value. I am guessing that long handles were originally intended to give the user more reach, and more power. So I think that handle length is really up to you and some experimenting will let you find the one you like (of course this means you need about 4 axes just to get started, ha!). You mentioned clearing brush and weight, so I really think you're on the right track with the boys axe. I would most definitely rock it with the 28 inch handle that will be on it. You may also find yourself pleasantly surprised at the splitting capabilities, though it's gonna shine less if you want to split rounds or stubborn wood. If you go the vintage route, my favorite axe is 3lbs on a 28 inch stick. Handy, but capable. I think the thing to focus on for the learning curve is accuracy while splitting, over power. For brush clearing there are lots of useful videos out there (US Forest Service videos I think on youtube) that talk about safety in that respect.
