So, FOR ME, I feel that climbing with 1 stick vs. multiple sticks is a wash, I feel it's pretty much the same energy expenditure, efficiency, etc. I don't care if you are climbing a telephone pole or a tree with multiple branches, the climb is going to be similar.
Where one sticking TRULY shines is the descent (if you are rappelling that is.) I've made some pretty sketchy climbs with both methods, the difference is, the descent with multiple sticks, in the dark, when it's wet, and cold, and stuff has started to freeze up, and you are fiddling around with aiders coming down, you ratchet up the sketch factor immensely. Couple that with the fact that I hunt alone 95% of the time, or more, and I wanted a safer option. Enter one stick climbing and rappelling. Coming out of the tree in the dark, cold, wet, maybe ice or snow is a piece of cake. No more worrying that I might slip and jack myself up a mile or more in, alone and the only thing my wife has are GPS coordinates (and I love her to death but she is somewhat directionally and geographically challenged).
I am just as lethal with multiple sticks as I am one sticking, but the exit from the tree is the true litmus test as far as I'm concerned, and the one stick and rappel method can't be touched in that regard.