I dont yet own a FL that runs on more than 1-123, so I dont yet have the option of using an 18650. I could buy RCR123's, but so far I just buy inexpensive 123's from batteryjunction for $1 - $1.45 apiece, and they last a good while. But I'm considering which 18650 light to buy now, while flip-flopping on whether to buy a Sunwayman Ti+ first. There are too many choices, not too much money.
I'll probably buy the 18650 light first, and I'll have several battery options then. I could keep buying 123's, or buy an 18650 charger and batteries, or buy RCR123's and a charger. I'll need to make a choice of which to get and use. I will always have 123's lying around, so that'll probably be the back-up option.
Which batteries do you run your 18650/123 flashlights on mostly? Can you list the advantages of 18650' vs. RCR123's? Will most of these lights also handle 16340's?