I own the first gen Jet III Pro ST which can only take 18650 cells. The version you are referring to can accept both 18650 cells and CR/RCR123s. Hence the 'BV' meaning 'broad voltage' as 18650 cells are 3.7 volts each whereas 2xCR123 = 3 volts each totalling 6 volts and 2xRCR123s are 7.4 volts.
The version you are considering can handle those different voltages, making it very versatile.
What you will like about the Jet III is that it is completely customizable, each of its 3 modes can be programmed to suit your needs and you can balance output with runtime, higher modes obviously eats more juice right? so tone down the light when you dont need so much light.
Get rechargeables and a charger, it's a one time cost which will pay for itself in time trust me on this. Head over to the marketplace and check out
AW's sales thread. for cells. The cells that can fit your needs would be the 16340s (get the protected ones) and the 18650s.
the 18650 have higher capacity than 2xCR123s so they will last longer.