it really depends on his body build... arent those reigning type bloodlines? He may have that thicker stockier body...that is meant for reigning and barrels and ranch work.
If you are showing in the big breed shows, it might matter, but depending on his way of movement, he may be able to do all of that stuff... He could be pretty versatile. If you are showing in more localized shows, I say do what you want. Otherwise, what you can do is figure out what suits him best and focus on that, then bring in the other stuff and aim for an all around horse. No reason you cant have the best of all worlds....
"Be a best friend, tell the truth, and overuse I love you
Go to work, do your best, don't outsmart your common sense
Never let your prayin knees get lazy
And love like crazy"