Five of us (60s, active, semi-fit) are debating this route in September, with the rest of the trip mostly sorted. The original plan was train to Genoa, then fly to Naples, probably via Rome, as there seem few direct flights. But someone knows someone who has a friend who thought the train trip SML/Rapallo-Naples is much better. Any opinions?
What is your question... whether to fly from Genoa to Rome/Naples, or catch a train? Your intention is far from clear.

If you are going to take the train to Rome to fly to Naples, that makes no sense, it is quicker taking the train, especially when you account for getting to and from airports.
For train ties in Italy check www.trenitalia.it, if you trip is more than 3 months away just put in dates closer than that. The train takes about 6hrs 30, and will have at least 1 change, normally in Rome.
From Genoa there is a direct flight with Volotea, booked in advance it might be cheaper than the train. But even then taking into account getting to Genoa airport and the time you need to be there, and then from Naples airport to where you are going in Naples, there will not be much in it door to door.
Yes: that was the question. There doesn't appear to be a huge difference in cost or duration - flying would be a little quicker and a little more expensive. Is the train trip particularly scenic?
Thank you #2. The alternatives are train from SML/Rapallo to Naples (via Rome) or fly Genoa to Naples. I thought the Volotea direct flight was only at sparrowfart (= very early) making it unpleasant to get to Genoa from SML in time. I'll check again.
All Italian train trips are (a) pleasant and (b) very scenic, the first time.
If there isn't a lot in it (time/cost wise) then I reckon the train is better.
Thank you for that #1. I have had a less than pleasant train trip out of Rome but that was in the '70s - and at least it was on time, which prevented it from being more unpleasant.

I think it depends on the day, the date i checked the flight is at 12.35. But to be honest it is more comfortable on the train and if booked in advance can be reasonable, the faster trains in Italy are now very comfortable and if you select the option with 1 change they are both Freccia trains some of the best in Europe for me.