Better outside in our neighbourhoods where it can be admired and seen by us all. Regardless of social status, financial viability, time constraint, nor location, 'cause there it is right outside your door!
If you're lucky enough you'll live in a place that has some excellent examples of freedom to art! If you don't then move! or start you own freedom to art!
Now, I'm not talking about you taggers,you vandals with a score to settle or an anarchic point to prove. Destroying all that can be written on, with a symbol or a name just because, just because it's a train or a bus or any other public service that they think it's ok to de-face. At least if you are gonna de-face it make it look better than it does or don't bloody touch it!
This of course is not what I'm talking about!
I'm talking about a true artist, a true creator of ideas & questions, selflessly showing the world artistic expression with nothing needed in return. I have to add that I in no way condone mindless vandalism, taggers (you know who you are *arseholes!) but you can see and feel the difference. The proof is in the pudding so they say!
It's a shame that to some people, spray artists & taggers are one of the same. Its clear that they both have very clear objectives & both want a reaction of a different kind. The spray artist is all about creating something nice/cool/funny prettifying the neighbourhood, a distraction, a reaction from their work whether polemic political, funny, Whereas the tagger, the vandal is still working out how to write its own name! Whilst getting a reaction from the system. Down with the system! I can sign my name to that!
Whereas art from a spray artist is beautifying the backdrop to our lives. Bringing a cheery smile to an otherwise dirty, damaged, derelict wall or doorway.

I found a beautiful example of this from Bristol homegrown 'West is best' Banksy in the Gaza strip..........
www.telegraph.co.uk/culture/banksy/11436286/Banksy-in-Gaza-Street-artist-goes-undercover-in-the-Strip.html
To those guys and gals out there fighting the fight.
Sharing their gift with the rest of us.
A spray can in both hands freeing their art.
Giving a welcome distraction, with a positive reaction.
ThankU
I salute you!