I won't claim to be a battery geek. However, I have spent most of my adult life dealing with electronic products, many of which are strictly battery-operated. So, I've had to learn the hard way what is important and what is not.
In general, you will get totally different performance from rechargeable batteries versus primary batteries (one use). For some products, one makes better sense than the other. Some products don't care.
I've used probably six or eight different brands of AA-size NiMH batteries recently, and I don't see any big difference in performance. One might have a few more mA-hours than another. Some have a little higher self-discharge (which is bad). However, for how I use them, self-discharge is a non-issue, because I use them up within 24 hours of recharging. Some batteries have better cold performance than others.
I have a camera external strobe flash which takes 4 AA batteries. Then there is an extra battery pack that holds another 8 AA batteries. This is intended to supply a maximum of current for quicker strobe cycling. I have maybe three entire sets of 12 batteries, so there are about 36+ batteries lined up for the charger sometimes. The important thing is that some batteries can be recharged quickly, and some are quite slow. Some chargers can handle the quicker charge rate, but some batteries will overheat when you do that. In general, you will get a longer life out of a rechargeable battery if you recharge it slowly, like at 1/10th of the maximum discharge rate.
Then for an emergency or high-priority device, I always keep one or two sets of lithium primary batteries on hand. They are a little pricey (one-time use) but they have very good specifications.
I thought that you would get a charge out of this message. :-)