Just to be clear, the 600 was a front engine, rear drive vehicle, while the 600 Multipla was a rear engine, rear drive vehicle. As such I'm not sure why the front engine 600 would need the traling arm suspension of the Multipla, but perhaps it gave better handling than the usual solid rear axle of the day.
The Multipla is cuter in person than the second photo might suggest. Aerodynamically, as Chrysler engineers found out in the 1930's, a car with a blunt nose and a sloped rear end slips through the air more easily than the other way round. Has to do with wake turbulence, I suppose. You can see that concept on most prop driven old airplanes, as well. Blunt nose and tapering tail.
The owners of the car at Good Guys said it had a top speed of about 40 mph, and leaned a lot in the corners. The web site for the other car (first pictured in this thread) says they did a fair amount of suspension work, and added (or upgraded) shock absorbers that resulted in better handling. From what I gather, the Multipla was a hit for small businesses in Italy that needed a delivery van type of car, and the six passenger version was also popular with big Italian families that could fit everyone in albeit with a further speed penalty.
The forward control nature of the Multipla isn't much different than that of the VW microbus or the later first and second generation Chevy vans. One definitely doesn't want to be in a head-on collision in any of these vehicles. I have a '67 Chevy Van that I love, but I do exercise extra caution in traffic or on roads where obstructions (deer, motorcyclists, etc) might pop up at any moment. Of course one can't anticipate every hazard but that's life isn't it?