Only you can answer whether to take the bigger but higher cabin or stay in the smaller but lower. How much more (factor will do, not necessarily $) are they asking for the suite? How tolerant are you of motion at sea?

I was on a crossing the other way (Portugal-(2 nts) Azores- (6 nts)-Florida - omitting the Rome-Portugal portion and I can tell you the middle of the western Med can be quite rough!) a few years ago on a much smaller ship, HAL's Prinsendam (~30K GRT vs Epic's 156K GRT) and it was rather rough (lots of pitching). One couple we got to know cruise that route quite frequently to get from the U.K. to Bermuda (flying home from Florida). The woman wasn't very good with rough seas and they had to get a downgrade from their higher deck window cabin to a lowest deck (which is difference of only 2-3 decks on that ship IIRC) one as she suffered motion sickness otherwise.

I wonder how many cruisers could have tolerated this voyage that I was on?