I have a 40 L Waeco 12V with 240V adaptor which has been great and supplements the van fridge most of the time but if we are going to do a good bit of bush camping, I have a 3 way purchased from Aldi for $299 which is realy good and very efficient on gas.
If I just had to have one I would have a 3 way but if you have access to power or can keep your battery charged the Waeco or Engel compressor models are much more efficient than the evaporative models.
The difference between Waeco and Engel is like arguing Holden & Ford. They both have their supporters and detractors. My personal choice is Waeco.
Regards
Paul