Well, not to sound like and "expert" or anything, but it was my tractor that bent the 3pt arm....
First off, this is the second time that arm (lower right) has bent. First time I snagged a root with the scar bar of my Gannon Boxblade. Didn't realize it was a root and thought it hit a rock. So, I lifted the box up. Yup, the root was on the outside scarifier and it torqued the assembly enough to bend the arm to the inside. Heated it and pounded it back into place. It didn't bend again for 3-4 years, until I pulled a log. Well, most of a tree really. I ferget how big exactly, 25 feet and in the 40's on the stump end and 30's on the small end. Hard Maple. A couple pounds. It wouldn't go very easily if at all dragging the stump end into the ground, so I picked it up and it went really pretty easy. The extra weight on the tires was very helpful. The butt end of the log was bouncing off of the draw bar, so it was in close.
Is it "better" to pull from the draw bar? Well, that is what it is there for, so I guess so. The draw bar is under the axle centerline, so the tractor is much less likely to flip over and crush you to death. But, that log would still be at the bottom of the hill or would have had to be cut into 100" lengths, before dragging if only the draw bar was used. Lifting the butt end off the ground makes dragging much easier. A logging arch would have been the hot ticket.
I think that the log swayed a lick and put some lateral force on the arm. And that arm was weakened to begin with. It probably wouldn't have bent if the arm was fresh and it certainly wouldn't have bent if it was cut to 100" lengths. Also, the lift arms were still in the back holes, giving the most lift height. (was using the post hole digger and needed the clearance, forgot to put it back, my bad.)
So seriously, don't worry about it. If you use the 3pt, use the holes that give the least amount of lift and don't get crazy with the size of the log.
jb