The mechanical carriage- running sky line set up, could possibly be a little more work for the hooktender, but in my opinion the most productive for logging our short (restrickted) units here in CA. I think the motorized carriage would be ideal for skidding distances over 1,500 feet.
I agree about the climbing, I do climb, but most the other hooktenders around these parts don't. Years ago when i was a rigging slinger, my hooktender never pulled hay wire far enough to get any lift, so we would ground pound the log out! Then i learned to climb and he had me rigging lift trees for every road line. I knew it wasn't always neccesary but, I got paid extra for it and he was the boss. So up I went. I have rigged lift trees for many years, and never topped one. Why do they do that up north? I am one of only a few climbers I know that still climb with chain. I started out with a nice rope set up, then I had to rigg a 10 ft old growth redwood for a lift tree, and my rope was too short to make it around the tree. So I rigged up with 40 ft of chain and up i went. I discovered it was much more user friendly then the rope and never looked back. I know its goofy, but its what I like.