Bonding or veneer for a dead, grey front tooth?

I am 19 and a few years back I got an infection in my tooth root and needed a root canal. This lead to the tooth becoming dead and grey. From that I have had internal bleaching done, on two separate occasions but it didn't really do the job - or was only effective for a short amount of time. I am very very self conscious about it (& an actor!) and want the problem sorted once and for all. What is my best bet since bleaching didn't work well enough - a veneer or bonding? Thanks!