Street as that is what I grew up with, I have ridden natural as well but it does terrible things to my nails and hair! Plus I have to clean this stuff, I think it's called... mud, off my bike it's just not for me! For rider progression you would have to ride both, riding natural for 1 comp season improved my riding more than if I had just bummed about on the streets for the same amount of time, but I like riding the street furniture for the look on people's faces, it's making the humdrum and boring an exciting challenge, (like how free runners view the city) it's just easier walking out my door and going riding. Unless you live in a field!