I went with my 27" during my first trip to japan, totally regret it! me and my friend were sitting together with this poor japanese guy who's by the window. and we had 2 large luggage in front of us. no legroom for 2.5hrs and when he had to get down, we have to move out together with our luggage. and it's super inconvenient esp when the train is crowded and there's only that much time for him to get off.
it's either you courier it to your hotel, or you don't bring such a big one. from that experience, no larger than 24", which fits nicely on the overhead. i also try to bring the luggage down early so that i dont cause any inconvenience to others. and even if i were to put the luggage at my seat, the person in front of me can still recline and all, so it's not as bad.