I have no direct experience with the RC-C8. It's just been recommended to me by socalridier and others way back when I first started seeking input on a 'budget' light set-up. Never got around to picking one up, as I ended up getting a Trustfire rated at 510 lumens instead. The RC-C8 meets the bullet points of being less than $50 and run off of AA or AAA.

Also, I asked the same question about the runtimes between the 3xAAA and the 18650- the `18650 gets the nod in both output and runtime. AFAIK, all 18650 cells are rechargeable, but some are 'protected' and others aren't, as well as capacity will vary.