Though the FAQ didn't specifically recommend either Red or Black 16340's over the other, most users seem to prefer the black AW ICR 16340's which are 3.7 volts - not the lower-voltage RCR123A's.
However, a quick bit of research finds that there are batteries out there labelled as "RCR123A" both in both 3.0 volt and 3.7 volt ... and some manufacturers refer to their products as "RCR123/16340" regardless of the voltage. Which might make sense to them since the packages are largely the same, but it makes things confusing for some of us since we can't even say, "Just use 16340's" and be sure someone will invariably find the right thing.
Another aspect of this (for some folks, not all, and not pointing any fingers) that I find frustrating is that people can become SO wrapped up in saving a buck or two on batteries, or frustrated with limited availability of specific makes/models, that they end up looking at stuff outside the recommended parameters and finding, buying or using products with incorrect specifications or not intended for a particular use. Not only is that confusing for all, it is time-consuming to those of us trying to ensure no one buys something they won't ultimately be unhappy with ... or worse, that is potentially unsafe.
Hopefully more folks can see now why it is SO much easier to just make one recommendation of what you KNOW will work well and be done with it!
Anywho, there are already several updates and add-ons to the FAQ. But I'm not going to do daily updates unless information is found to be drastically incorrect, misleading or unsafe (which I do not think is the case, yet). And I'm not going to turn it into a "Battery FAQ" -- there are already plenty of those out there if one takes the time to find them.
I will do a bit more research and thinking on how to make the battery section more comprehensive and clear for the next update.