Do what you want, it's your horse! :)
I personally would go with what's more practical. If you plan on showing a discipline that requires button braids, then I'd roach rather than pulling it to braiding length. I think a roached mane just looks so sharp on Fjords. But if you're showing a discipline that a long mane is acceptable, then I'd grow it out. Or do both! I used to pull my horse's mane for two shows and then let it be long for the rest of the year.
"He doth nothing but talk of his horses."