I chose using a skid steer attachment because I can use down pressure. I can bore holes without help (if I have to) and see the auger without twisting myself like a pretzel to see behind the tractor.
I remember using the 3 point augers on an old MF 65. The guy on the tractor with his body twisted 180 degrees, and the guy on the ground with a bar stuck in the auger pulling down to get it to dig, and if the auger got hung up you needed a big pipe wrench to back it out. With the skid steer, I just hit the hydraulics in reverse.
I bought my auger not long ago at an equipment auction. It was new on a pallet with 2 augers, I gave $2150.00 and drove away very happy.
It's up to you what you want to use, but the skid steer auger will save you enough in labor to pay for itself pretty quick in my opinion.