When it comes to the environment the Jet Fuel is no worse than gasoline.
However Jet Fuel is safer than gasoline and also means it has a higher octane rating and produces greater power and is also more efficient than gasoline.
The jet fuel and gasoline are very different for multiple reasons.
For example, jet fuels must meet strict requirements for flying characteristics such as flashpoint and freezing point, while auto gasoline is made to run through catalytic converters for pollution reduction, along with other factors.
Jet-A is used in a much higher volume than 100LL.
All the jet engine commercial aircraft each day burn through orders of magnitude more Jet-A than piston aircraft burn through 100LL.
That means that there is a much higher production volume, and therefore a cost savings as a result.
Jet fuel can actually be used in cars, but only in diesel engines.
Kerosene jet fuel and diesel are actually similar enough to allow for cross-functionality and would provide a similar performance.
Although, I wouldn't recommend running a jet on diesel.
Aircraft efficiency differs, as do the conditions on different routes—a domestic airliner can get anywhere from 45.5 to 77.6 miles per gallon per passenger, with an industry average of about 51 miles per gallon of fuel per passenger.