Ive used the Waeco CCF-18 -(18Litre) on a six month trip (West Africa)- and it was fine - I bought this as it was the right size for 2 people - without having lots of wasted space and I was in a Defender 90, so using a larger Engel was not really an option - just too big.
The fridge/freezer performed flawlessly and was on every day except 2 - in 6 months pretty good - coped with corrogations no problem and 50+ degree heat in Mali. If you have plenty of room and enough cash, go for an Engel, if not the Waeco's are pretty good - maybe not as well insulated, but very usable.
The best setup Ive used is Twin starting batteries in Parrallel (for starting, winch, work and spot lights, etc) and then a split charger to a Third (deep cycle) battery for the fridge and flourescent lights and anything else that could be left on and potentially flatten a battery.
I could run the fridge/lights for 2-3 days with no problem whilst in a camp site. I also took a small trickle charger that I could use at camp sites to keep the deep cycle battery charged if we were there for longer - so I didnt have to static run the vehicle. I was able to get electricity at a few camp sites no problem (for free)- so it WAS worth taking a power lead and travel kettle ! - also it meant I could charge my camera battery up with the charger locked in the vehicle - quite handy.
Ex Drago Driver, LRE Instructor,
LR 90 300 Tdi Overlander
Suzuki DR650 Overlander
..and Bloody Nice Bloke!