let me disagree here :-)
The problem with Winch ropes are not ONLY cuts/wear and tear from having the rope rubbing against rocks/trees etc (which is the biggest problem of having a synthetic line) ... also the fact that mud water gets inside the rope will wear down a rope --> if mud and sand get in between the individual lines, they act like mini razors, cutting their way through your precious synthetic lines ... I have seen MANY Dyneema lines brake while they didn't have any surface/visible defects ...
The ONLY winch rope I would recommend (because of the above) would be a winch rope that has a full protective sleeve over the Dyneema ropes itself ... I have posted this earlier: the only ones I know with these protective sleeves are from MasterPull
http://www.masterpull.com/cpage.cfm?cpid=478Looking at the price, add a few hundred dollars compared to a normal Dyneema rope :-)
From my point of view: if you are not doing any competition, there is no real reason to go to a synthetic line ... if you however want to go for synthetic line, go for a line with a protective sleeve over the full line ...
The steel cables, with correct maintenance (take of the line + grease) have a very high liftime ... I have heard (not seen) of them braking as well, but mainly because of bad maintenance ...
My 2 cents ...