I can't speak to the Olight, but I have the Xeno E03 and can tell you it's an amazing value for the price.
I have mine with an XP-G R5 cool white. Great light for a single AA. It really pours out the light on a 14500 though, although I'm sure the emitter is being overdriven.
A real nice touch on the E03 is it comes with an extra clicky switch.
As you may or may not be aware selfbuilt did an outstanding review on the E03.