As someone typed in the 707, 727, 747, and 75/767. I just have a couple of comments. I only ever did Dutch roll in the sim in the 727 and found it a difficult recovery. The 707s I flew had yaw dampers, but in the sim recovery seemed much easier. I also flew the KC135 for many years. It didn't have a yaw damper, but did have a rudder axis for the autopilot. Take offs and landings were of course autopilot off and it was always funny to watch new guys Dutch roll their way down final. We also had to be able to air refuel autopilot off.
As far as longer or shorter planes being more stable I vote for longer. The 747-100/200s that I flew were very stable. The SP was very much less so.
My favorite narrow body plane is the 757. Going out of Denver on a hot day in a fully loaded 727 was a little much for my old heart. No problem in a 757 though. Also never had to go full power in the flare to avoid planting it.