Mine seemed like #6, tiny.
Before putting on my winch I redid my starter, alternator, main fuse link, frame ground, and motor ground all with #2 wire with ends crimped and soldered. I only use pre-tinned marine finely stranded cables. After rewiring the power systems in my boat I really like the cable so now I use it on everything. Being pre-tinned really helps with corrosion as well. My buddies and I do lots of big boat battery systems and #2 is the minimum gauge cable we use. Length is a big factor as well, if you add a load or source that requires more than 10' of cable I would step up a gauge so you don't lose any voltage. With 20' between the batteries and the loads on my boat I use 1/0 cable. Its way overkill from a ampacity standpoint but it is helpful to maintain those critical 0.1 or 0.2 volts that would otherwise be lost.
When it comes to something like winching you can easily and quickly overload the factory wiring systems. Sure they work fine when they only need to supply high current for a couple seconds to the starter but winching is a completely different load. One other benefit is bring able to start in gear or use your starter motor to move the Jeep a short distance. The heavier cable will supply more voltage under load as well as avoid overheating.
