Some horses need shoes, most don't. It of course depends on your horse and what you are doing with him or her. Are you riding a lot? What type of terrain? Is your horse sound without shoes? If the answer to the last question is yes and your farrier and vet see no reason why you should shoe then keep him/her barefoot.
I know that there are some folks that have strong opinions on barefoot only horses but I always put the horse before my opinion. What does your horse need? It is a very good chance he/she won't need shoes but again, vet and farrier will let you know that. For that matter, your horse will let you know if they are needed or not.
If you need them, you need them. If not, then don't. I've noticed that many people shoe their horses just for their own piece of mind, and in turn the horse suffers for it. Why do you feel that you need to make the decision? Something change about your horse? Lame? New discipline? These all play a factor. Personally, I believe the majority of horses can do their job better barefoot, but I do also see the need for shoes in certain circumstances.
My horse has great hooves and I ride in soft terrain so I have not used shoes but I took a lesson and the instructor suggested shoes to help my horse break over better and she did move much more balanced with shoes.