For a LED flashlight，300 lumens or 400 Lumens？Which one is better？
Depends. As always.
You’d be hard pushed to tell the difference! If the 300lm light has a cool tint and the 400lm light is warm, the cool will seem brighter. If the 300lm light has a tighter beam and the 400lm light a bit more flood, then the 300lm light will seem brighter. So yeah, depends.
The correct answer is 100 and this should be in the alkaline battery section.
350lm.
500lm
Over 9000 lumens!
You can never have too many lumens, but its all about control, the modes and the UI backing it up.
2000
You’re all wrong.
42.
Yes, but what was the actual question again?
42 is correct.
The question was wrong, too 
One or the other. Not both. They’re too close to be two modes in the same UI.
I bet you wouldn’t even notice a difference between 300 and 400 lumens.
Potato.
It can’t be 2000, not mathematically possible.
If all other factors are the same, and there are a lot of factors, then 400 lumens will appear 13% brighter than 300 lumens.
Most people won't notice the difference.
Please also note that a lot of flashlight sellers lie about the specs so you have to do your own research and not just trust the marketing.
Yes
Another response:
What do you get if you multiply six by nine? 
42
Just like 2 + 2 is 42
(4 = 2 + 2 and 2 = 2) 