Either works fine, but as IceWaterBong87 said, mylar is easier to clean up and IS more reflective. I personally use the mirrored mylar on the walls of my grow rooms and paint the ceilings with Kilz --- so far I've had fantastic results with that, but I use a 600w HPS for flowering and a combo of CFL's and T12's for vegging in another room. You should be OK either way though, especially with a smaller grow room. If it's a large area I'd definitely recommend Mylar due to increased reflectivity.
Good luck, and good growing dude!!!!