We stayed in Naples for 5 nights in 2002 (?) and, whilst we enjoyed our visit, would not rush to go back.
We visited Marco for a day and felt it would be a bit too quiet for us to want to stay there.
Now, we are definitely not party animals who want razz-a-ma-tazz night life and entertainment on our doorstep! By "too quiet" I just mean not enough to keep us occupied for more than a few days - we're not good at sitting around a pool.
In Naples, we found the centre a bit too sedate (I remember mainly expensive antique shops and art galleries). However, we visited the shopping mall, Tin City, and went on an airboat ride in the Everglades (I highly recommend booking this - we thought there were so many places doing this that we'd be able to just turn up, but they were all fully booked and we had to return the next day!). One of the highlights was lunch in
JT's on Chokoloskee - definitely not your average tourist restaurant! I also agree with the recommendation for The Bubble Room, although we went there a few months ago and it seemed toned down and a lot less 'interactive' than our previous visit (hopefully just an off day

).
On Marco we really liked the buffet lunch in The Snook Inn, overlooking the water.
We drove up to Naples from the Keys, and then went on to Orlando, so I don't know about the drive from Miami.