Just to close the loop on this, I had a good discussion with Glenn Danuser in April about choice of bits, and eventually ordered the EP6 with a 10" cast auger through a local dealer. I have dug just a few holes so far and this is what I think:
The EP6 is looks well made. It has a cradle so you can travel without dangling the auger. It is pretty small, actually the smallest hydraulic auger that I've ever seen, but that's about all you can do on a 9 gpm tractor. The offset QA mount works well, it is easy to see the auger/hole by leaning over just slightly to the right. I've seen guys with skid-steers dig holes and basically clean 'em out, but I'm still learning to use this thing and have been leaving anywhere from a few inches to a foot or more of loose material in the bottom of the hole. Being able to reverse direction is great, I got the bit stuck between two rocks, tried to lift it out, would not budge, and then reversed direction and it came right out at low rpm. If you are looking for a hydraulic auger that will run a tractor with less than 10 gpm, I'd say include this one in your evaluation.
As far as 3 point vs. hydraulic, it probably depends on your ground conditions and budget, but I definitely like the hydraulic units.