An extra 150-200€ for PE over normal economy is a no brainer for such a long flight and you make up for some of that with the extra miles, though if you search the forum you might find that some doesn't like the hard shell seat for sleeping.
An extra 600€ on the other hand is a different story, and it boils down to how comfortable you are in an economy seat for such a long trip, I know I would be fine for a day flight but not for a night flight for example.