While the size and weight (mass) of a vehicle does play a part in braking distance, several other factors come into play, such as:
Yes, smaller cars will stop sooner than a heavy truck, but what if a small car is filled to capacity with heavy supplies and the truck is empty? Then the brake times would be much closer together. Jeeps come loaded with safety features, so as long as you are an attentive driver, the braking distance generally won’t matter.