I commute year round so I ride in the dark a lot, and from my experience you can't have too many lights! The more you have, the more visible you are to motorists. The advantage of the helmet light is that if you turn your head towards a car, the driver can't help but see you - saved me from getting run into from a driver on a side road one time. I'd recommend a bright white light on the front of your bike as well as the helmet light. You can position the bike light so that it provides good illumination on the road directly in front of you and the light on your helmet extends the range further out ahead of you. And as I already mentioned, the helmet light lets you illuminate things to your side as necessary. In addition, if the batteries on one light go out you still have the other light. Good lights are expensive, true, but considering the cost savings over driving your car, they pay for themselves pretty quickly - and the cost is nothing compared to the value of your life!