regular roadwork > treadmill
not really, it depends on the goal..for me I am not good at keeping pace and time. I just want to set the pace and not have to worry about anything, turn on the TV and maybe watch some music videos, before you know the cardio session is over.
plus also I have bad feet! I think that I have high arch or something, when I run my calves and shin get really tight and start to hurt.