Nice wide bright flood light for the bars that will last a couple of hours at least and a nice bright spot for the helmet that will last for a couple of hours at least.
Often the lumens quoted refers to the highest setting which may drain the battery fast, so you are unlikely to be riding on that setting all night anyway. Depends on the lights. Some just have low and high, some low, medium and high.
And then comparing quoted lumens is useless. They are mostly rubbish figures, and if Chinese, just plain ludicrous. Anything like 5000, 9000 etc, just knock a zero off that and it’s more accurate.
Other than that, in a group, get whatever the other have or brighter 😉