When looking at light options, there are a few things to consider besides the obvious weight and cost considerations.
Handlebar vs. Helmet Mount
For most night riding, a single light is adequate and it’s possible to get away with fewer lumens if the light is mounted on the helmet rather than the handlebar. This gives the rider the ability to scan further up the trail and look around corners, something that isn’t possible with a handlebar mounted light.
The downside of having a single helmet mounted light is that, in order to produce enough light, the weight on the helmet can be significant, especially if the battery is also mounted on the helmet.
Many light models have cord extensions that allow for the battery to be carried in a camelback or a jersey pocket but even the added weight of just the light on the helmet can cause excessive movement of the helmet on the head, especially on rough descents.
On the other hand, a bar mounted light can be heavier without added discomfort since the weight is on the bike and is less noticeable. On trails with few corners or on dirt roads, a floodlight on the handlebar is generally fine.
For racing, most riders will use both a handlebar light and a helmet mounted light. The exact ratio of the lumens from each light is dependent on rider preference but there are generally two schools of thought.
Some people enjoy having a bright floodlight on their handlebars to illuminate the trail directly in front of their bike at all times and use a smaller helmet light to be able to look around corners and farther down the trail on high speed sections.
Others prefer a weaker handlebar light to keep the trail immediately in front of the bike illuminated and use a bright helmet light to be able to see far down the trail.
Rechargeable vs. Standard Batteries
A second consideration when thinking about lights is the difference between a rechargeable battery pack and a light that can run off of AA or AAA batteries.
The lights with higher lumen outputs tend to run off of rechargeable battery packs and are perfect for racing situations and night specific rides. The downside is that the batteries tend to lose charge over time, so it’s possible to carry around a rechargeable light and battery pack for the entirety of a summer only to get caught out on a late fall evening and find that the battery is dead.
For long multi day rides and races such as the Arizona Trail Race a light that can run off of batteries easily purchased at a gas station is more useful than one that needs a specific charger and outlet to recharge.