I prefer to have my satnav set with 'direction of travel' always to the top .A screen orientated to portrait would show further ahead. But no big deal, and certainly wouldnt influence my choice of car. But all other things being equal its a gimmick that may tip the balance for a few.
I think its illegal for an infotainment screen to show TV, Movies, games etc if its visible to the driver. Any swivel angle that would allow only the front passenger to view them would be quite severe, and require software that provides TV etc, but only when the screen is angled. Not sure if it exists. Without the ability to show movies TV etc there is no point in having an angled screen as the passenger can see and use the existing screen easily