I wondered this same thing, and luckily, we don’t have to guess or use theoretical physics (more mass means safer). IIHS records the actual, real-world driver death rates by vehicle category. The safest vehicles are not the largest based on deaths. Mid-sized crossovers (SUVs if you prefer) were the safest from 2011-2014. Larger SUVs have come back to be slightly safer in the most recent study. And the Lexus RX is the safest vehicle, period. Longest stretch of time with zero driver deaths. 4WD and AWD crossovers usually have a lower death rate -even when comparing the same model. The Suburban is not a safe vehicle, relative to other SUV choices, if driver death rates per mile driven are your gauge. Here is a summary from 2016, and here is the latest data available. Habits and driver ability count for a lot. Still, a 2WD suburban has a driver death rate per million registered vehicle miles of 60. The Lexus RX AWD had a rate of zero (and outsold the Suburban by a large amount). In between, there are many great choices.