After buying a Nitecore TM16, I read several reviews of the Acebeam K60 and wanted to really compare both lights, so I purchased an Acebeam K60.
The K60 heats very quickly, especially in the area of the adjustment ring. That area is hot when the fins on the head are barely warm. After 2 minutes when the K60 steps down on level 6, the adjustment ring is almost too hot to touch, but can be rotated if you do it quickly. The fins on the K60 head heat at a much slower rate. The TM16 heats much less in the area of the switch. I suspect that the plastic reflector on the TM16 uses a trick employed by Kodak on slide projectors. The Kodak trick was to use a dichroic reflector coating on a plastic reflector that allowed visual light to be reflected but infrared heat to pass thru. With a conventional metal reflector that effective and clever method is not possible.
I expected to really like the battery carrier on the K60, but find it is a lot more trouble and slower than just dropping the batteries in on the TM16. The battery carrier adds complexity and weight. Aligning the pins on the TM16 cap is somewhat difficult but you get better with practice.
The flat regulation of the K60 is much better than the continuously declining output of the TM16 at the highest level. The TM16 has an area of declining output at the end on all levels. The K60 has absolutely flat regulation at all levels except for the timed two minute drop down on level 6.
The variable frequency strobe of the K60 is very effective. The light reminds me of my Jetbeam RRT-3 (SST-50). The variable frequency strobe plays crazy tricks with your eyes and is superior to the fixed frequency strobe of the TM16.
I am using Samsung button top 25R 20A 2500mAh INR batteries in both lights for best performance. The beam intensity on my TM16 is about 135000 Candelas measured at 5 meters. The beam intensity of my K60 is about 155000 Candelas under the same conditions. The TM16 output is voltage sensitive, the K60 is not. Measurement on both were taken with the batteries fully charged using a Extech EA33. The central hot spot on my K60 appears slightly dimmer in the center. This is apparent when moving the beam sideways, but barely detectable when the light is stationary.
The TM16 voltage indicator in the switch is a nice feature. The TM16 will not work with flat top batteries, The K60 uses either flat top or button top batteries. The Nitecore TM16 is widely available at US dealers. The K60 is not widely available at US dealers and is usually ordered from dealers in Hong Kong or China.
Both the Nitecore TM16 and Acebeam K60 are excellent high quality flashlights, very similar in output and size. Hopefully these observations will help you decide which is better for you.