There are a lot of variables. Common wisdom would say a wider tire would be slower and heavier but, having a larger footprint, be easier to manage and be safer. I found that the 50mm Schwalbe Big Ben tires I am now using are faster than the 42mm Marathon Dureme I used to use. They also make it much easier to ignore the surface. I'm a lot more likely to take a two track or gravel road than ever before. At this point I can't see a reason to use anything else.
Marc