there is no right or wrong answer to this question. Street art can be any form of graffiti art or even pasties including some of the artwork that Banksy does. www.banksy.co.uk/
There are always going to be fine lines between these two hemispheres and it is up to the creator to decide what their style revolves around.
Graffiti is a form of self expression and in no way should be seen as some kid coming out and being destructive. There will always be graffiti artists and street artists of different kinds who are looking to leave their mark upon the world.