What are the advantages and disadvantages of using a micro USB rechargeable lithium-ion battery versus a rechargeable lithium-ion battery that requires a battery charger?
One advantage of the micro USB rechargeable lithium-ion batteries is that you do not need to purchase a separate charger for these batteries. However, they are a little bit longer and don't work with all Fenix flashlights such as the Fenix PD35 V2.0. Also, the protection circuit in the USB rechargeable battery can sometimes interfere with flashlights that use multiple batteries like the TK35UE. They also take a bit longer to charge than through an AC powered battery charger.
The lithium-ion batteries that do require a charger will work in any Fenix flashlight that is compatible with that specific type of batteries so you don't need to worry about little quirks like with the TK35 that we mentioned above. However, you will need to purchase a battery charger to charge the battery. If you already own a charger we recommend getting a non-USB battery. Keeping things simple is often good!