Its a question of price vs current at the led.
The Terralux drop ins are 500 mA approx at the led and $25. The Malkoff, if available, is 1A (in a 3D) or twice as much and around $70. It is substantially brighter than the Terralux (I've used both) and will not dim if you leave it on a long time because it has proper heatsinking.
Otherwise, build your own and you can push an SSC at bit higher but at some risk of problems, especially if push too hard and lack the tools to do electrical and temp measurements. But that's more $.
The Malkoff is the premier drop in at the moment and it matches Gene's modded mags that he sold prior to the drop in. But the Terralux is a good buy.
The Terralux likes a 4D with a 3D as reasonable. The Malkoff runs best in a 3D but will in a 2D still outperform the Terralux. Unless Gene has started to make and sell C drop ins, his first drop ins do not fit a C light.
Racer7