On anything other than a perfectly smooth road, give me wider tyres any day. Narrow tyres have to be run at ridiculous pressures to prevent pinch flats, and as such might as well be solid in terms of bump absorbing qualities. Given that most bikes have no suspension other than the tyres, running a wider tyre at a lower pressure gives you a better chance of not shaking yourself to pieces. Remember too that the more the bike rattles around over bumps, the more chance there is of a wheel lifting from the road- not something you want when you're going round a bend at speed.