For a three point auger, the only thing that is important is the cutting teeth. Gear boxes and other components are all the same, or close enough to not really matter. If you want to spend big money, then it's all different with hydraulic, but that's another topic. After going through three different brands, and struggling for years drilling in hard packed red clay, I finally gave Country Line a try. I'm not a fan of Tractor Supply, and I regret that now because that is the best digging auger I've ever seen by a huge margin. It doesn't matter how hard the clay is, it just digs right through it. The teeth and tip are replaceable, but so far, there hasn't been any noticeable wear.
Now for the negative. It digs "TOO GOOD" You will have to buy a very large pipe wrench and a length of pipe to slide over it because sooner or later, you will bury it into the ground and not be able to get it out. The trick is not letting it dig too fast, because once that happens, it will bury itself into the ground and you're stuck until you unscrew it with the big pipe wrench. I had a cheap 36 inch pipe wrench that I busted when this first happened, then I found out my dad had a very old 36 inch pipe wrench that is indestructible. My guess is they used better steal back then, or it's just a higher quality brand, but either way, it takes a lot to unscrew a buried auger.