I hate to be brand specific, but for the terrain that my horses have to go on and the type of conditioning I do they have the right rubber density to suck up that concussion to keep my horses safe. All of my horses are barefoot and it works for us. They do get some conditioning done while barefoot, but for the most part I cannot afford to be looking for that rock with our names on it. I have been doing my own shoeing and trimming for the last 15 years of so, so I am very comfortable working on feet and giving them the proper barefoot trim.
I don't know if you ever had a horse that just grows heal, but I did. That was back in the day when I was shoeing. I am not sure but don't think you can build a horse to compete at the upper levels of endurance when his feet are not the same angles all the time. The advantage that I see that the barefoot horse has, is just that, their feet are pretty much the same all of the time. My horses get at least a weekly look at there feet before applying boots, making sure that the toes are backed up enough and that the heal is down where it belongs. Takes a few seconds of care and the ability to handle the hoof file to keep them in perfect balance.
There is a learning curve to anything worth doing. I have suffered the learning curve and still do on occasion. It took me a couple of times to get Ambrose's feet where I was happy with them and into the right size boot. He is now down a size from where I originally started and they fit perfect.
There are lots of tricks to working with the boots and it can be a headache for sure, especially if you are not capable of working on the horses feet. There is lots of information out on the Internet, so you just have to look and learn.
Bottom line and the purpose of this post is that at least for the type of training that I do and the terrain that I condition in there is no way that you could or would do that in steel without hurting your horse.
My horses train either barefoot or with the Gloves on, once in awhile I will Glue on boots for a week or so. MONK has raced in the Gloves, he did two back to back 50 mile rides at Desert Gold. They worked great but because I seem to have so much to do when I get to a ride I did not like having to put them on in the morning when he is all AMPED up, so will more then likely GLUE on boots before I leave for the ride.