Suitcase vs. Backpack in Tokyo trains

Keep in mind you are bring what you've got all over the place. If you choose a suitcase, i am sure it would be fine if it fits as a cary-on for planes. You can go bigger, but it can become a hassle. Try to avoid rush hour on trains in Tokyo! You will definetly feel the weight of your luggage.

Suitcase, hands down.

Once i traveled with a backpack and it was not convient. I could see how it could be if the backpack is small but ginourmous ones are in everyone's way.
I travel with small suitcases now(wheels optional), and most people i see do the same. There should be an elevator or escalator in most stations.

it is a good idea to have your hands free when maneuvering around stations and crowded areas. I found it much easier getting on and off crowded trains.

BACKPACK!- if you can hold it all and more. Japanese trains are comfortable and quick, but small. Try to pack light- it is just easier traveling that way.