Well just got back and have to say a little biased towards the Engal
Found the primus a large and bulking unit that when in the car very hard to get to the control panel to adjust , also had a few times when the plug came out it went back to -18c and froze everything . Well we thought we had sorted this out but when we stopped over and put it on 240 it again reverted back to -18 . Lost a few beers so was not that happy.
The first thing I would do is cut of the plug and fit a engal with a much longer lead to it .
Also the wireless temp gauge was good and worked well but it takes up a 12v socket and not enough Ifeel to dedicate to a fridge temp gauge . I take a engal hard wired one anyday.
The drain was good as we had a few spills'
It is noisy
They are a lot cheaper and we did not have that many problems on the way back , but by that time we had 2 nights with dinners frozen on arrival and all beer frozen , so not think the Primus never recovered after that.
Did not do cool down times with both as the engal stayed as a freezer the whole trip , and cool the both down on 240 before they go into the car. Ran them both of a Thumper in the back of the car which was being charged while driving , find this better than using car socket as runs all the time and does not kick in and out at stops.
Anyway just my thoughts