From my reading, and I'm trying to put together a list of differences (Malkoff MD2/M61 vs. Surefire G2X Pro):
Hi/Low Operation
Surefire's dual output is at the tail switch: "Dual-output tailcap click switch—press for momentary-on low, click for constant-on low, return to off then press or click again for high".
Nice one hand operation, but lots of clicks to find what you want. I assume no momentary high, but that doesn't make any sense, so maybe the way I'm reading this is wrong. I personally like the one hand operation.
Malkoff's: "High/Low is controlled by head rotation. The On/Off switch is a forward clicky with momentary function."
Need two hands. Not sure if you can over rotate the head (loosen too much by accident). This is good if you want a set/forget simple operation.
Tail standing
Surefire = No.
Malkoff = yes for an extra $15.
Batteries
Surefire = CR123A
Malkoff = CR123A/18650
Runtime/Illumination
Surefire = 200/2
Malkoff = 170/5
Someone already mentioned the 200/2 vs. 170/5. 2 hours is plenty, 5 is better. I have a Fenix P3D and never complained about runtime with my rechargeables.
Price
By the time I add everything I want for a Malkoff...it becomes real expensive (2x the price of the Surefire).
Other
Surefire anti-roll.
Beam shots
Surefire = Unknown.
Malkoff = Excellent.
For me it is going to come down to operation and the huge price difference. Surefire is a lot less, and I like one-hand operation.
Illumination and runtime is important, but I typically run on low and occasionally on high, therefore I don't go through many batteries (I also use rechargeable).
I'm leaning towards Surefire. Waiting for beam shots before I make final decision.
Jake