The standard dynamo generator setup is to power both the front and rear lights off the same power source, using parallel wiring.
You can replace the dynamo with a rechargeable battery. I use a battery stuffed into a waterbottle, so I wire it how I like.
LEDs are bright, but often very directional. Dynamo lamps seem to appear brighter from all directions. ESGE/SKS fenders come with a rear lamp/reflector unit.
The best rear battery LED lamps are the ones that mount under the rack. They are bigger and brighter.
I always use a dynamo on tour, so I dont have to worry about keeping a battery charged. How do you manage your battries ?