The Nikon used a single Nikon design lithium battery with no specific power guarantee. Out in the remote parts of Australia, I could not buy an extra battery. It would require a 3 day drive to a town then a few days wait while a battery is flown from a local city. I would have to start a trip with the absolute maximum number of batteries I would need for a day and make sure every one was charged every night. $990 is too much to pay for batteries to run a $900 camera.
The Olympus uses 2 generic CR-V3 (also called LB-01) lithium batteries with no specific power guarantee. The CR-V3s can be replaced with 4 rechargeable AA NI-MH batteries ($20) or 4 AA alkaline batteries ($5). Out in the remote parts of Australia, I can buy AA alkaline batteries at the local town and local towns are rarely more than 2 days drive away.
I can get 10 sets of AA NI-MH batteries for just $200, an amount I consider reasonable to run a $900 camera.
If you think that batteries can be hard to get in country Australia, consider one place a visited a few years ago. That place was only half way toward the remotest part of Australia. The residents visit their local city only once per month because the town is 8 hours away. That is 8 hours by aeroplane.
The first rule with batteries is to buy batteries that are on sale in every shop in every country you visit. AA batteries must be the world's most common batteries. Small cameras can run on 2 AA batteries. Large cameras may require 6 or 8 batteries. You can get radios, torches, flash guns, and DVD players that run on AA batteries. Use the one type of battery so you can rip the batteries out of the DVD player to run the camera when your camera's batteries are dead. You never know when you will be the only photographer standing next to the bridge where some royal person is going to crash.
The second rule is to buy easily rechargeable batteries. Some mobile telephones (cell phones in America) have rechargers that work in cars. Few cameras have the same type of accessory. AA batteries have cheap readily available battery chargers that work from car batteries, solar power, and every mains power in the world. You can even get little wind up rechargers.
If you buy a digital camera for more than just a toy or very small prints, buy a camera that uses easy to buy generic rechargeable batteries.