The smaller one is of course adequate if all you need is to recharge batteries.
We found that the Kimberley area can get hot during the day in Summer but not so much in the Winter months.
Peter (ATV42) says he would prefer to go to a caravan park for air conditioning if it is hot. That is well and good if a caravan park is available The times we have used a generator for cooling has been either on a very remote road, camped up after a day’s travelling, and only needing cooling for a couple of hours until the sun sets, or say crossing the Nullarbor. Recently we pulled into a delightful camp off the Nullarbor and at 2pm it was nearly 40 degrees. We ran the aircon until 4pm when a cool breeze came up.
Even if a caravan park was available we would much prefer that lovely bush camp anyway, despite needing a generator for a couple of hours. And much cheaper to run a generator for two hours than paying for a caravan park for a night. Plus the attendant nuisance value of booking in, unhitching etc.
The generator gives you options.