I own both.
Overall, I enjoy the E1B more.
However, my Olight experienced many problems, but that was only because I realized the LED components had come loose in the head, which I fixed by tightening everything up with special needlenose tweezers. Also, the Olight M20 beam quality is utter trash. I own BOTH the smooth and orange peel reflectors, and the orange peel reflector is actually just as trashy as the smooth reflector. The beam profile is almost as horrible as all Rayovac flashlights in existence. (Brutally honest here, because companies who put out garbage for which people spend their money, need to suffer the consequence of a bad reputation...for putting out such horrible lights).
On the other hand, I also own the M20s. Now this is a great light for you to consider. I own the original M20s. I'm not sure which LED is has, but it is NOT the 2nd-gen M20s, which cnotains the "S2" LED. Anyway, excellent beam, 4 modes, slightly greenish-blue tint, but it will make you happy in almost all areas.
E1B makes a great EDC (every day carry) or backup light, but it is certainly not a camping light. Best of luck.