My advice would be to get yourself a Tirfor or something similar and a snatch block, if your budget is a consideration, and not overlooking the weight factor either.
Yes they are slow and can be bloody hard work, but coupled with a snatch block it will almost certainly get you out of most situations, they also have the added bonus of being able to pull you out backwards, which a conventional front mounted whinch can`t.
For a bit of self assurance, have a look through most of the previous overland trip reports, and see how many of them actually used a winch on a regular basis, most of them are used on the odd occurance.
Check out this site, these two went looking for trouble, and still managed most of the time with a hand winch.
Personally I think if weight or space was`nt an issue one of each would be perfect, but its not really realistic.
An aussie escaped from london, now in Dubai.