In the above photo;
Lumens = luminous flux
Candela = luminous intensity
Lux = illuminance
Lumens (luminous flux) is the total amount of light a source emits in all directions. A bare 100-watt light bulb emits about 1700 lumens.
Candela (luminous intensity) is how bright a light source appears to the eye as a point source. The 100-watt bulb is 1700 lumens, but is easy to look directly at because those lumens are spread out all around the bulb (low luminous intensity).
On the opposite side of the spectrum from the light bulb is a laser - very, very low lumens but is very tightly focused into a very narrow beam. Lasers are eye-damaging bright even though the total output of light (luminous flux) is very low.
With flashlights, lumens only tells us the volume of light it produces. If a 650 lumen flashlight has a broad, even beam its luminous intensity (candela) will be low. If those 650 lumens are more tightly concentrated into a narrow beam, its candela (or how bright it appears to someone looking into the beam) will be higher (in some cases,
much higher).
Thus the question becomes is what is the light going to be used for? How do you want to "spend" those lumens - to illuminate a wide area or to to reach out and light-up an object far away?
The light I posted above is "only" 650 lumens but those lumens are tightly focused into a 70,000 candela beam, making much more like a laser than a light bulb. It can reach out a very long distance to illuminate an object, or can be used to overwhelm the vision of an assailant. The tactics for using a light configured this way are pretty well documented.
So I carry two lights - one with a wide, general purpose beam for administrative tasks and the "light saber" for "stabbing" an assailant in the eyes.
I hope this explanation helps!