If we're talking about Japan, Hoshido might sell more b/c of its Japanese theme, though FE veterans would prefer Nohr. Not to mention I heard Nohr has higher difficulty than Hoshido, so amateur players would want to play the easier one. But I have a feeling Nohr is going to sell better in NA/EU.
I would pick the Hoshido route. Aside from a few characters, the Nohr characters don't really catch my attention. And the Nohr classes seem really bland to me. But I really like a majority of the Hoshido characters and their classes, so Hoshido it is.