Would you buy a heavy 4x4 for safety reasons
 

You might think, if unfortunately you were involved in an accident with a small Kia, you would not come of worse in an accident if you were driving a really heavy 4x4.

Are you speaking from experience here?

No, neither am I 97 years old

Many drivers think they are safe in a 4x4 but due to their height and weight distribution they are more likely to topple over as a certain gentleman found recently.
In a straight forward collision many factors come into the equation such as air bags.
I was unfortunate enough to have been involved in a collision whilst driving my Jaguar XF where I was side swiped by a VW Polo
The curtain airbags saved me from injury to to my head whereas if I had been driving my 75 I would not have had this protection.
The steering wheel airbag was not deployed in my accident, only the side (curtain) airbag.
Amazingly the Polo survived obviously after repairs but the XF was a total write off.

Couldn't agree more Jim, these SUV designs are very vulnerable to flipping over.

Youtube and the like are full of video clips of accidents where they flip, some surprisingly easily.

Worryingly they advertise these style of cars as great for families.

Luckily, Daisy Duke was nowhere to be seen at the time! :D Also, luckily, no serious injuries for all concerned. Metal is replaceable.

The tyres on modern cars also make them easier to turn over as the grip levels are very high . Old cars with skinny crossply tyres would just slide.

Any vehicle will turn over if a sufficiently hard impact changes its direction of travel and thus its centre of gravity enough. Just have a look at the Russian Dash Cam movies on You Tube. I've always had a 4x4 of some description but that's more to do with more predictable handling when there's something other than dry tarmac under the tyres.

Was it not Top Gear who crash tested 4WD and found them to be less safe than normal saloon cars

A few years ago a neighbours daughter was involved in a headlong collision between a corsa and a range rover. There were 3 fatalities in the corsa and no injuries in the range rover.