I'm no expert but work in a hiking/outdoor shop and have tested a number of head torches from various leading brands, the two that realy stand out in my experince are:

1. EOS by princeton tec
this one has a top quality case & switch which have out lasted all the other models in terms of warrenty returns. In fact we have never had one come back so thats a good sigh. other popular brands including Petzl (no offence to Petzl owners, they are still great lights!) have a lot of problems with switches, pivot points and cases. the EOS also has a microchip that regulates the light output so you get max. out put over a longer period of time. other brands slowly begin to fade immediatley from the begining of use. to top it all off the EOS has a water proof seal (must lubricate the o-ring to keep seal integrity) this makes it great for surving big rain storms or quick dunks during river crossings.

2. Petzl E-lite
this is an aswome little light in its own right but is also great as a back up. it weighs 27 grams, is also water proof to 1 meter (2.2 feet? sorry I'm an Aussie)and can withtand a wide range of temperatures. also the batteries can last unused in your pack or in a cash for 10 yrs. plus it has the red led thats handy for reading a map at night and not totaly destroying your night vision.

I havent seen, used or tested any Doug Ritter lights but I'm sure they are also top quality. I have used both of the ones I mentioned above heaps and they work great.

Hope some of that helps!