I have a 26" Dahon Jack I take with me folded on Metra in Chicago. I won't say that it is super easy to get on the train but it's not as bad as you would think. I would have to find a space for it between the seat and a wall for example - I have some straps that would allow me to store it overhead but i haven't had to use them yet. Most everyone has been willing to move a package to let me fit my bike in at rush hour - most are impressed to learn about a folding bike not having seen them before, particularly 26 inchers. I used to have a 26" Bazooka Navigator and I like their bags that clip on the handlebars, unlike the Dahon you have to wear like a backpack - my "office" is a backpack so that wouldn't work for me. Finally I use the same bike for leisure riding and as a bigger person myself - weight not height - I can't see a 20" bike being that comfortable for me. My two cents.