OK, I'm an old school PNW conifer climber, and the first half of my climbing life I spent predominantly on gaffs, better than half the time. Out here, if you are gonna climb a real tree, you are looking at 2 to 3 inch bark...and if it's a really real tree, twice that...'til you get over 150 feet or so up.
So I was weaned on 3+ inch gaffs. And didn't change them when I had the occasional red alder or big leaf maple to take down, thin barked as they are. I never had a bit of issue dealing with the long gaffs. I dunno...I have heard many a skilled climber say that in thin barked trees, long gaffs are unstable, hard on their ankles, a bad choice all around. But frankly, I was never bothered by them in those conditions. Maybe because my experience in old growth conifers always included both extremely thick bark in the lower half of the tree and gradually thinning bark higher up.
Bottom line, for me there is no question...full length tree spikes all the way. I guess if I lived somewhere where all the trees where thin barked, I might have decided differently, but I'll tell you, when I go to the SE states to teach climbing workshops, I climb on those long gaffs, and I don't get out-climbed by the locals
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The hooks fell out of my bag in a field somewhere. Never did find them. They were nice on thin bark live oaks I remove a lot of. I just use the long ones now until (if I feel I would like another set on shanks) I buy a new set to replace my Bashlins. 
I know there are lots of good climbers that use and are happy with pole gaffs . But when I started climbing we rarely set top ropes so it was always spur from the bottom up. When you are heading up a big, thick barked tree with no top rope, tree gaffs are the better choice. After a few years on tree gaffs I felt as comfortable with them in small wood as big, so never felt the need to change.
