The good news is there are many great options out there. The bad news is there are many great options out there.

I guess to each their own. I personally do not want an external battery pack (I want one small convenient package), and a mount I can quickly and easily add and remove without tools.

I want USB charging for my primary lights - Not having to deal with ANOTHER proprietary charger is worth real dollars to me. A backup or extra light can use regular old batteries (AA or AAA)

A quality and reliable product is also important to me, and if I can buy from a local/US company that is a plus.

Light and Motion looks very attractive to me as its a local CA company, seems to make quality products that meet my needs (with accurate lumens ratings), and I really like the side lights on the urban series. I also have a niterider that works quite well and is well designed. These are also brands I have looked at also as they are what my LBSs sell, and I do like to support them.

As for number of lumens - tarwheel makes a good point about the ambient light. I have noticed my light seems VERY bright in my back yard at even the low setting (~200 lumens???) but when in a brighter area with headlights, etc to compete I really like it on a higher setting to see where I am going clearly. If bright enough, the light is almost not needed to see, but important to make sure you are seen. Personally I think that the 500-700 range for max lumens seems pretty good, though I have found in many conditions a good 200 lumen light is OK.