of course, once it hits you it doesn't make much difference. However, the faster and/or more massive an object is, the bigger is the radius of damage that it can do, hence the more likely is for you to be affected by it.

For example, a sufficiently fast and massive object can derail and hit a large building killing many, while a 80Mph SUV hitting a building wall will still, most likely, not be able to bring down the whole building.