Thank you to everyone who responded above, and the overwhelming sentiment seems to be that it was a no-brainer to go with F, with one dissenting voice. I think, from a cold, economical point of view, Thichbay is probably right, in that I won't enjoy $143 worth of benefit in F over the $101 Saver fare (I will need to check a suitcase)—warnings about the restrictions of Saver duly noted—or rather, the same $143 could be spent to far greater enjoyment in a restaurant or elsewhere. However, whilst my brain agrees with him, my heart is inclined to go with everyone else. Aargh, and I was just about to pull the trigger on F!

Well ... it is almost 11 p.m. here in Rome, so I shall sleep on it, and see if any other opinions come in overnight.

P.S., Thanks also for the detailed analysis, djp98374. I was wondering why the fares suddenly shot up at the end of the week, but I shall be travelling on the Monday, so fares seem reasonable at this stage. And, in addition to the options you mentioned, I also see direct flights on Delta for slightly lower prices than AS, but I am drawn to AS simply for the lounge access, as I shall be travelling before the 15th.