There are variables: length of ride; how crowded is the train, and how crowded is it likely to become? Are you carrying anything? Is it winter, with people wearing large coats? Assuming that all the seats may end up occupied, 2 is the most compressed, especially if large people sit on both sides of you. 4 can also be cramped, hard to get in and out of, and with limited leg room. 5 is a little better, and people often sit at an angle to minimize foot conflict with 3 and disruption from entrance/exit from 4. 3 can get bumped by 5/4. 1 only has one other seated person to conflict with, and has elbow rest/room on one side, though if the train is crowded enough you can get squeezed from any direction. As noted, you want to avoid the bench in front of a map, but most don't have one. Overall, I prefer 1, though people getting on and off can be an issue when things are busy, but it's also easier for you to get out.