I found this interesting. I just looked up the top of the line 16.5i Warn and the entry level 10000k warn, and both have about the same amp draw at 4000 and full load, 200amps and 500amps, respectively. Your alternator will never keep up unless it's big enough that it has to stick out a hole in the hood. Your total winching time is pretty much determined by how much battery reserve you have. The alternator only does a minor extension of that limit, perhaps 5-10%. If the engine is not runable, the winch will still pull as long as the battery is not drowned out, for a while, anyway.

A hydraulic will pull at full capacity as long as you don't boil the fluid and the engine is running, or at least crankable (with the plugs out, the motor will crank fast enough to get some hydraulic flow and thus some winch action, slow, slow, slow, though).

For me, a hydraulic is the ticket. I want a winch in a hitch receiver cradle, so I can pull from either end, and I don't have large voltage losses sending all those 'lectrons for an electric to the rear, and the cost of that oh $o large cable, just two pipes and quick disconnects like a bobcat. My winch can stay at home for a highway trip, and live in the back cargo all the time, not messing up my air flow and stuff...