I'm in the minority, then. I prefer it darker. It depends on what you want to the image to portray. Is it a bright, shiny, colorful picture of art on walls? Is it important that people see every last detail? Or do you want more context: grafitti isn't really a 'bright and shiny' art form but it shows up in dark, gritty tunnels?
I like in the first picture how the left wall is much darker, but then there are patches of light on the right wall, and that's where the eye is drawn. It seems a more purposeful picture. I think it needs a bit more contrast, not overall lightening - I'd like the left wall a bit darker and the patches on the right wall a bit brighter.
In the shot that was lightened overall, it's unclear where my attention is supposed to go. The lightest part becomes the light fixtures on the top of the left wall. After that, the eye sort of goes to the end of the tunnel. Other than that, there's just a jumble of uniformly-lit graffiti on the walls and it feels busy.