Most winches advertise no load and load line speed, having a super fast no load line speed is great (I run a WARN 9.5ti and it is insanely fast) to get the rope back on the winch and get rolling again. The loaded line speed is significantly slower on a electric winch but some winches are still much quicker then others. Even though they are quick they are still very steady and I have never had a problem with a winch going too fast during recovery.
We perform recovery for off road races a few times a year and our big one is King of the Hammers every February, speed is very important here because most of the time we are recovering rigs in places that have only one or two paths through a canyon or gully. If they are stuck for too long huge backups are created and people aren't happy.
Another selling point on fast winches is adding blocks, when you need to increase your mechanical advantage you also increase the amount of line that needs to be winched in. With a slow winch you will literally be crawling along when using multiple blocks, you'll want the fast winch here.
Winching with your engine off:
With a good battery you can winch a bit without the truck running. There are those horror stories about the trucks that blow PS pumps and lose hydraulics and then you lose your winch as well.
Electric winches are also generally much cheaper and work well for our applications. When you get into the larger winches that need to operate more frequently (with a 100% duty cycle) the hydraulic winch will win hands down.