What plane type is scheduled? If we're talking the A359, I would rather take row 40 -- you'll have more legroom than any seat in PS and if you're talking A339 the same is true for row 42. I certainly woudn't spend $1300 extra dollars on the relatively short flight to Europe if the those exit row seats are open.

Where are you based? Assuming either JFK or BOS for the flight to FCO you're talking about ~7-9 hours in each direction. What's the cost to do Y in one direction and PS in the other? Might consider doing Y on the eastbound (because it's such a short flight you won't get much added value for the PS seat in terms of sleeping assuming you are able to sleep in a non-lie flat) and then take PS on the return for the longer daytime flight where the extra space and higher level of service makes more of an impact.