What are the advantages of using a battery grip over just carrying a second battery that you can swap out midway through your shooting session? I think one of the advantages of not having a grip is you can have one battery charging while you're using the other one.
Do I need a battery grip?
Posted 11 May 2014 - 10:52 AM
The battery grip makes is so you don't have to worry about swapping out batteries, this is very useful if you can't afford to miss a second of the action or if the situation makes it impossible to swap out batteries (when I photographed at a color-throwing festival, I had my entire camera wrapped in zip-lock bags with only the front of the lens exposed, and at an event like this with color dust flying everywhere it would be a horrible idea to swap batteries).
A grip also makes it a lot easier to shoot in portrait orientation with the dedicated shutter release and function keys.
If one is photographing a long event, it may make sense to have a charger that simultaneously charges two batteries, so two can be in the grip while two are on the charger, this makes it much more efficient to shoot at long events.
Lastly, battery grips will sometimes come with cartridges to use AA batteries in them instead of rechargeable camera batteries, which gives you more freedom with your power as you could swap a cartridge of camera batteries with a cartridge of AAs.