It kind of depends on the chassis' structure rather than weight. That being said the only thing more weight accomplishes is the impact is worse for anyone that isn't you.
It is better for the car occupants to be in a heavier car. IIRC, US road deaths of people outside the car have doubled over the last ~20Y because of the rise of the SUV and its ilk. European safety rules take into account people outside the car in the notion of 'safety'; I don't think that US safety rules do.