I think it depends on what you're paying for the Premium Economy (if the ANA is the one you're referring to); we got an upgrade option about 2 weeks before the flight where you can bid on the seats; we just put in the minimum (I think it was like $180 per person(?) per way) and ended up getting the seats. The food options I think were the same but they give you more dessert~ and the seats were better - I'm 6' as well.

So if you can get the upgrade for cheap, sure - but I don't think it's worth what they ask for when you purchase the tickets.