Don't do what the big devs are doing these days. They're all getting excessively lazy and putting no effort in, relying on normals, spec, and God knows what else to make things look good. If you look at some of the diffuses that end up in games these days, they're more or less just flat coloured. It might be easier and some people might actually think it looks better, but it's a bad habit to get into because if you do need to rely on the diffuse alone later on, you're fucked.