Stuart, I'm a little, well actually not a little, I'm actually a lot confused at what point you are arguing against, what point do you think I was or clearly very inefficiently was trying to make?
Your example above of the tragic loss of life, I don't know the specifics, but I'm sure that the inappropriate speed was a factor, again I'm not sure what point you are now trying to make.
Just so we are on the same page, I would be happy & compliant that around all schools & vulnerable areas the speed limit be reduced to 20mph, I would also advocate that anyone breaking this limit face severe fines/bans. I also believe that the fines/bans on drivers/riders in 30mph should be increased dramatically. I am fed-up of following cars down the de-restricted road into our village at 40mph only to see that when we get to the 30mph limit they speed away from me & continue at 40mph whilst I drop to the limit.
As I type this I think it's symantic's, I believe that speed is not dangerous, but inappropriate speed is, which could be 5 or 10 or lower mph on a motorway dependant on the circumstances, you on the the other hand appear that all speed is dangerous at all times, how you move around the world I'm unsure.
With regards to weight you clearly are correct in that instance, however that to me is a simplistic view, you are not taking into account air bags, ABS braking, traction control, tyre performance, geometry changes in suspension, changes in external surface matter. Were I to be in an accident in either car, I would prefer it to be the later model not the earlier one, but how that would reflect on somebody on the outside involved in an accident I'm not qualified to answer.
Last point, I am not aware (which doesn't mean it hasn't happened) of any car causing an accident, it is normally the driver or the person responsible for the maintenance (or lack thereof) that actually caused the accident, the car was just the vehicle (no pun intended) for the accident to happen.