I like the walls cuz i can just look up at a wall close to downtown of my area and find throw ups everywhere
Freights are the best because they go all over the country and are rarely cleaned so your tags will go everywhere and more people will see it than on a wall
Subways I would say cause a lot of people see it getting on and off, trains however just go on their rail, subways go all over city.
For me, freights are the way to go. Nobody goes bombing around here and I don't want to blow the cover by doing a piece in the towns near me. I don't see much graffiti around here, except some toys that didn't have a crew. All they wrote was kings and south/north side. Thinking of going over it, but I don't want the security to increase because of it. With freights, I never worry about it, knowing that they come in and leave.
Freights also are taken across the country sometimes and I don't have a subway nearby so I wouldn't know.
walls that are on on the track side are the best. trains will be buffed within 24hrs but my favorite is going track side bombing doing throwups on walls then having to duck and hide when a train passes by its good adrenalin rush