I have two recharging systems, the Energizer 15 minute one and the Rayovac IC3 15 minute recharging system. Both of them use NiMH batteries. The Energizers hold 2500 mAh while the Rayovac holds 2000 mAh.
As you'd suspected, the higher the rating the better. Well, supposedly they are better. I'm like you, I'm kind of skeptical of the knock off brands online. Who's to say they can't just put any old rating on them? That's why I stuck with the two name brand systems that I bought retail. It wasn't that much more expensive to do so.
I don't think you can find the Rayovacs anymore, so I won't bother comparing the two. You can still find the Energizers at just about every major retailer. If recharging time is important to you, be sure to buy the 15 minute recharger since they also sell a regular recharger that takes hours to recharge a set of batteries. They both use the same batteries, just that one charges them in a much shorter amount of time. And of course, it also costs about twice as much.
Here's a quick link to the 15 minute recharging system that comes with 4 AA's...
http://www.amazon.com/Energizer-15-M.../dp/B0000DIIAS
The initial cost is a little high compared to disposable batteries, but it pays for itself rather quickly. Keep in mind that these NiMH batteries will also outlast (Energizer claims that they last 4X longer) alkaline batteries by a ton. I don't bother buying regular batteries anymore, I just have about 40 rechargeable batteries around the house at all times in various devices. Haven't purchased AA's or AAA's in years.
Hope that is of some help to you.
**EDIT**
I don't think there are any real reliable Lithium Ion AA or AAA recharging systems out there. Those AA or AAA Lithium Ion batteries that you can buy retail just really aren't made to be recharged.
**EDIT AGAIN**
My comment about no name brand recharging systems was not aimed at the Maha system someone posted above. I was talking when I was looking to buy a system 3-4 years ago, my decision was based on name brand and reputation. If someone has experience with a lesser known name brand, please post about your experience. I'm all about buying cheap as long as it works!!
**EDIT YET AGAIN**
One last thing to address. Ni-Cd (nickel cadmium) rechargeable batteries are old school technology. They won't even last as long as alkaline batteries per charge. Stay away from those!! You'll only frustrate yourself using those. If you're interested in how the batteries compare, read
this.