Having owned both here is my comparison. It may be somewhat unfair to compare a light released a year ago with one released just a week or two ago but it looks like the PD36R Pro is one of Fenix’s best selling lights and is still definitely the flagship in their PD category, it seems unlikely they’ll be releasing an update any time soon so the MH12 Pro is definitely one of its competitors.
The Nitecore is apparently based on new technology and a new LED that their sister company have developed, which is cool.
The main obvious difference in terms of performance is that the Nitecore is more of a thrower and the Fenix is a more floody beam, 63,500 peak candela vs 36,600 respectively. The Nitecore achieves 500 more lumens and 125m further throw. Both lights achieve around 900-1000 lumens consistent output on the High setting, with the Nitecore running for approximately 30min longer than the Fenix (4h 30m vs 4h).
Other differences that may be less obvious are the Nitecore is lighter - 153g with the battery vs 169g for the Fenix. This may not sound like a lot but the Nitecore immediately felt light in my hand. It’s also 7mm shorter than the Fenix. Another significant difference is that the thermal protection is much more aggressive on the Fenix - turbo mode doesn’t last very long before kicking down to high to reduce heat. The Nitecore on the other hand will sustain turbo for significantly longer and consequently will produce a LOT of heat - enough to burn your hand if you touch the head, and enough to make holding the light even the natural position with fingers just below the head uncomfortable fairly quickly. Personally I prefer the Nitecore approach here as it allows more control, if I’m cycling with the light mounted on my handlebars then being able to use turbo for longer is a benefit and heat isn’t really a concern.
Speaking of cycling - both lights will fit nicely on the Fenix bike mount which I recommend. The Nitecore has a new protection system where it will detect close objects and kick down the power to level 2 to avoid burns at close range. If fitted with a diffusor head, which I like to use when cycling, this happens immediately but can be overridden by simply increasing the brightness with the switch.
The Fenix has dual tail light switches, one of which gives instant strobe access, whereas the Nitecore has a tail switch and a side button. The Nitecore has tactical mode vs EDC mode and extra strobe modes (Beacon and SOS) whereas the Fenix just has the one mode with the brightness levels and strobe.
The Nitecore has a completely new more aggressive grip pattern on the barrel of the light which makes it much gripper, particularly if using gloves.
Both lights come with similar accessories, both lanyards are usable although I prefer the Fenix adjustable lanyard as it’s slightly longer and the adjuster felt more robust. These are available separately from MyFenix if you email them and ask.
Build quality on both lights is superb and although the Nitecore doesn’t come with a lifetime warranty like the Fenix, I have no reason to believe both wouldn’t last until the LED wears out if handled sensibly.
Ultimately it’ll likely come down to which beam profile you prefer as the Nitecore is much narrower (although still with useful spill). My choice was to keep the Nitecore and sell the Fenix but both are excellent lights that demonstrate the state of the art.