Inside the wall or outside the wall?

[ejm1961Tbird]

I am in the planning stages for a detached 30x40 stick built, with insulated walls and drywall in the garage. My questions are about running the electrical grid and the air lines. For the electrical grid, I would rather have everything running in the walls. Put in boxes every three feet all the way around and plan ahead for lots of power. However, some people would prefer to run the wires in conduit on the outside of the wall. What say you? I would also like to have a clean look for the air lines, but I could see running these on the outside of the wall. I could foresee problems with air line leaks at some point, and it would be a real PITA to have to rip into the drywall to find the problem. Your thoughts on this too?

Thanks in advance,
Ed