If you’re just taking into consideration their performance, synthetic rope and steel cable are pretty close to one another. However, if you don’t mind paying a bit extra, go ahead and get the synthetic rope.
The synthetic rope is simply easier to work with. Once you’re done using the winch, it’s easier to re-spool the rope compared to the cable. Plus, you can tie synthetic rope back together should it snap. The same cannot be said for steel cable.