Masaki, I don't think it much matters unless you have a balcony. Even with a window instead of a port-hole (E and D), it's more fun being out on deck looking at the sights.
But this means that you are "out and about" more, walking, with a breeze in your face!
I will have my own balcony this time on the Diamond, but on the PG, I've twice travelled "E", once port, once starboard, and loved both.
