Hi Mike,
Team Recovery does not involve using winches, it is a ropes only event.
I've not done that much winching - perhaps someone more experienced will post here, but this is my (possibly blinkered) view. Most people that use winches that I know use them for one of these 3 reasons:
1. To enter winch challenges around the country (rarely done at elrc) which is an orienteering style challenge where you collect punches using a card attached to your gear lever. Typically these have to be road legal to drive between nearby sites.
2. Occasional club events: Not necessarily road legal vehicles, used at ELRC winch events, and sometimes at the National, say 4 events a year?
3. General use for either recovery at play days, trials, setting out, or even an unfortunate problem while green laning

I don't know of anyone with one for loading onto the trailer, as Karl says, a £25 hand winch mounted on the end of the trailer does the trick nicely.
Most of the time, the more you pay for a winch the faster the line pull is, and the more reliable it is, so if you are ultra competitive, you would go for a hydraulic winch (fast), or a top of the range electric winch. As you reduce the price, you will have a slower pull, especially if you have to use a snatch block to reduce the ratio.
James.