I don't really see the point of buying a bigger car for your own safety. What is the point of you not being injured if you just killed someone else. You might be physically okay, but you'll be mentally scarred for life.
You're also ignoring the case where the other driver causes a crash, and dies, but you live. Sure, you're probably still not going to feel great about the situation, and may suffer some emotional issues, but I don't think too many people would say they'd prefer they were in a smaller car and died instead.