Leather soles are great for slipping into and out of stirrups. If you don't ride horses, they're great for slipping on your ass on carpet, stairs, wet grass, gravel, and many other common surfaces. My balance and coordination are good enough that I never slip or fall, except when wearing leather soled boots. I finally just accepted the fact that if I'm going to buy a pair of leather soled boots, I budget in the cost of new rubber soles and I take them to my shoe guy before I ever wear them. They've make thin Vibram lug soles that give me great traction, which I want from anything on my feet. Leather soles wear out really quickly too.
As you've read, there are a lot of brands which are all good quality, so the distinction between them is largely personal taste and comfort. As for leathers, gator, croc, caiman, and ostrich leg are my favorite looks, but there's nothing wrong with plain leather, especially when you see the price of exotics. Lizard and snake look great but don't hold up as well if you're rough on boots.