It depends first on the horse and their hooves. Many, many horses are perfectly fine unshod or just using boots when needed. Others do better shod due to various factors. Your best bet is to educate yourself, talk to knowledgeable farriers/vets (many of them, not just one), and to first and foremost LISTEN TO YOUR HORSE.
My boy is shod during the summers, I've considered boots, but they freak me out so I haven't yet go that way. We were barefoot for 3 years before I put shoes on him. Three years of limping down all of the gravel roads (basically all we have to ride on) and him ditch diving constantly to get off the hard ground. I was constantly told "oh, you just need to condition him to it!" How do you condition a horse to hard ground that literally cannot walk 10 feet on a gravel surface without limping?
I had a well recommended barefoot farrier(actually tried a couple of them), I tried trimming on my own (with guidance), and so on and so forth. He isn't fed grain, isn't overweight, and isn't stalled. However, he is kept on soft ground and ridden on very hard and gravelly ground. We are also "trapped" by snow/ice for a good half of the year, so no hard ground to be found then either. Unless I was significantly more wealthy than I am there is no way to condition my horse to hard/rocky ground. So I shoe him when it becomes necessary. The pony ended up being shod this summer for the same reason. The difference between the ground they are kept on and the ground they are ridden on is enough that their hooves cannot acclimate fast enough for the relatively short season we have. It is possible their hooves would acclimate, I definitely have no doubt the pony would, although I am not sure that the gelding would at all.
Now, my old horses that were kept the exact same way? Never shod and never a lame step in their lives. Although they were given straight corn and all sorts of other terrible things and never had an issue. Apparently they were just tougher than my current two.
Bottom line is listen to your horse and educate yourself from a wide variety of sources. There are very few absolutes in the world and most of them have nothing to do with how to keep your horse.