Significantly less paperwork for one. You can form an LLC with a single sheet of paper in some states. No separate tax forms to file. Any losses pass down to the members, which is especially beneficial when you are starting since lots of startups(in fact any new business) will probably have losses. I am not an accountant, but I think you can also offset income from previous years if your losses exceed your total income.

Edit: I'm not too familiar with the S-corp election for C corps, so most likely most of the pass-through benefits apply there as well.