The oem unit is a balance charger designed to work with the oem Parrot battery and does the job. It charges at a higher rate than would normally be applied to a Lipo battery and some think this could shorten battery life but I don't think it's been proven. My biggest beef is not with the charger but the oem battery. It has a protection circuit that can cut power if voltages get too low and cause the drone to drop out of the sky. This could happen in marginal situations where the battery is already at low voltage, cold and under high load.
As I also use aftermarket batteries I like to use an Imax B6 balance charger as it gives more control over how the battery is charged & allows me to do a storage charge, which the oem can't do.
BTW I'm no expert. This is stuff I've picked up on the internet & personal experience. If the drone's under warranty then I would keep using the stock charger. If you go on to use an aftermarket battery, that's a good time to get a suitable balance charger.
There is a good video on how the stock charger works
Mick