I've been running the Befco for about two years now. The teeth move, but the fingers don't. I trim along 4 miles worth of walking trails with the bar in the vertical. This thing will cut through branches and saplings up to 1 1/2 inches easily as long as you are not in a hurry. It will also cut through branches and saplings a little over 2 inches if you're willing to sit there and let it gnaw for a minute. I think it leaves a pretty good, smooth cut (YMMV). I also cut around the edges of my 2 acre pond. It seems pretty heavy duty to me.
It was a little pricey. $5000 installed with the extra hydraulic lift kit, but I expect to use it on these trails for the next 40 years. That works out to $125 a year (assuming it lasts that long). Well worth it in my book. Befco also sent a complete, extra tooth bar.
I got the 7 footer. I've got more reach than I need in most places. Also, with the 3ph all the way up, I can easily cut branches over my canopy. My 45 hp Kubota handles it easily. In cutting hay, it works fine. You do have to be VERY patient. If you go too fast, it will bind up.
I'm happy with the Befco.