Was looking for lights a while ago for commuting. Found the MTBR light shootout really helpful.
Quick glance without in depth article reading.. my vote goes to the L&M 500
Here:
MTBR shootout page: http://reviews.mtbr.com/category/lights-shootout
Backyard Beam Comps: http://reviews.mtbr.com/2012-bike-li...pattern-photos
Trail Beam Comps: http://reviews.mtbr.com/2012-bike-li...pattern-photos
L&M 500 mtbr test: http://www.youtube.com/watch?v=u5x2BeaoErY
Serfas 500 mtbr test: http://www.youtube.com/watch?v=nopDUg5XQV8
Also, I don't know what you're looking for.. meaning, are you looking for as much light as possible with a small foootprint? Do you want to be seen as well as see?
I went with a Dinotte 600 for both front and rear tailight. Since I was commuting I wanted to be seen (tail) and to see .. even if it might be raining. It has a decent size footprint. It's not tiny but the ability to see was worht it to me. I did try Dinotte's 200 and it was excellent as well but really worht the upgrade to 600 to be able to see potholes in enough time on rainy nights. Oh and both have sizeable battery packs you have attached to your frame somewhere. It's not the lightest solution either.
Anyway, hope this helps...