Welcome to Cruise Chat,
It doesn't appear any balconies have an obstructed view on the Grand. So your only concern with a guarantee would be if you minded being all the way forward or all the way aft. Some people have a preference for midship. I have been located in all areas forward, aft, midship and never had any problems. The payoff for taking a guarantee is a lower rate and it works great if you don't have a specific preference of location. Booking late you may not have as good a choice though with assigned either.