it really depends where you live and how visible it is.. mine would be at the bottom of my garden and well away from prying eyes, so wouldnt be too worried. besides the concrete ones are a bit
I used to have a really old refab garage in Hull and the local scumbags used to just 'peel' the metal off the door. personally i reckon a good strong timber door is as good as a steel door.. my house door is timber after all.
karl