I think that there is a definite difference here between handling and pure aesthetics.
So whilst the consensus seems to be leaning towards 20mm on the rear, the front comes down to whether you want it look good at the possible slight expense of handling and to a very small degree, increased load on the suspension, bearings etc. (This is always quoted as an issue and basic physics means it must make a difference, but unless you go really wide I doubt it has a huge effect on component wear)
I did stick some 10mm on the front at the same time as I put 20mm on the rear, but I felt it made the handling less precise, with less feedback and more likely to follow ruts in the road. This is a personal opinion though. Others will differ.