The article below presents a sound strategy for allocating investment funds between a Roth IRA and a 401k. Here it is in a nutshell:

1. Contribute enough to the 401k to get the full employer match
2. Max out your Roth
3. Go back to the 401k and put in any remaining funds you can afford

This assumes you can contribute to a Roth and have a 401k to contribute to.