Honestly, IF you can afford to get both, you WILL be able to sell whichever you do not like and recuperate the cost.
The Rodent 6 is notably longer than the Fehrman which might make it more useful for batonning and such. The Fehrman may be heavier and handle-heavy due to the handle design compared to a customized R6 - FFG and no top-guard, that Rodent 6 should balance perfectly right at the index groove. What finish will each blade have? Satin will trump coated for drag-reduction in deep cuts through again e.g. cardboard or splitting wood with a baton. I am not sure which knife will be thicker behind the edge, but edge-geometry and edge-finish (coarse vs ultra-fine) will trump chemistry in wear-resistance. That said, CPM-3V should be more wear-resistant if cutting abrasive materials like cardboard, and should be tougher too, but SR101 isn't your everyday carbon steel - what Busse does with 52100 seems to change its performance level.
Honestly, it really should come down to COMFORT in use + performance. Unless the cutting performance and toughness of one is leagues ahead of the other, the one that is more comfortable in your hand, more comfortable in use, is the one you'll prefer. I've sold-off nicer high-performance knives because they weren't as comfortable in my hand as something with lesser steel or slightly worse geometry. Sometimes it's easier to alter edge-geometry than handle shape (if you have to grind), and the former usually won't void your warranty, whereas the latter...
zcd, which handle is more comfortable?