I was on the Island 10/7. I took the Ocean to Ocean tour. If you really want to see the who canal this is the tour to take. It is a whole day. Goes through the cut and out to the Pacific. Going through the locks in a small ship is amazing. The owner of the small ship is very personable, proud of his ship. They gave us a very nice bag lunch and there was plenty of fresh bottled water. Shop went under bridge of the Americas and into bay of Panama.
I talked to some people who went on the train tour. They thought it was fair. They did not get lunch even though they did not get back to the ship until 4pm. Be aware that the RR is not always along the edge of the canal. So you do not see the cut. I dont think you see the locks on the Pacific side. At any rate you certainly dont go through them.
Even though the bow of the small ship is crowded with people looking at the locks; the O to O is an outstanding side trip and I think far superior to a RR ride.
Just a personal opinion based on my experience and talking to other cruisers/