I put most of my money into my regular 401k, but I still put a couple percent into the Roth 401k to give me more options at retirement in avoiding higher tax brackets. The contributions to the Roth 401k counts against your overall 401k limit, the only difference is that the Roth 401k money is after tax and comes out tax free, but you probably already know that. It's just nice to have money in both buckets during retirement, but you also have to weigh the current tax implications and just make an informed decision.