Kubotaman, For the material I dig...stuff that has some clay mixed in with some loose stuff...an edge with no teeth doesn't go as far or as well into the pile as one with teeth.
also, the stuff kinda hangs on all the way out to the edge of the teeth, doesn't fall thru the teeth (dry sand would do this)..thus, extra capacity in the load.
My objective is to get a heaping bucket load, each trip with only one dig into the pile. For what I dig, to get a heaping load without the toothbar, I often have to dig into it, back up and dig into it again. This takes extra time. With the toothbar, 95% of the time I make one scoop and it comes out heaping and the excess falls off on all sides.
So, net net, with a toothbar it takes fewer digs into the pile to get a heaping full bucket, the scoop of material has a wider bottom because it hangs onto the toothbar lip and sometimes over the lip and this results in a wider overall scoop base and a taller stack. My estimate, unscientific I agree, is that I am 30% more efficient in loading my dump trailer with the toothbar than without. I have not done a timed study but I know that on the occasions where the toothbar had been removed and I worked on loading the dump trailer without it...it was painful and I REALLY, REALLY missed the toothbar.
There have also been numerous times when the toothbar provides just the extra needed to hold a load... like the garbage cans I carry from the shop to the pickup point.
Oh, yes, I've used the toothbar on numerous occasions as a secure lip to place under a trailer frame and lift it so I can change a tire. The regular lip just doesn't do the job nearly as well, or at all depending on the frame.
Unless you have personal experience with a toothbar, you've kinda just gotta trust me that it is a superb addition and extremely useful. It gets in my way only when trying to get an extremely smooth surface on something. For this, I unbolt the toothbar, turn the blade slightly down and back up.