I read a summary of a DOJ study a few years ago that actually looked at how crime victims protected themselves, and looked at the rates of injury each defense produced.
Fighting back with a gun produced the lowest rates of serious injury to the victim- the rates were lower than no resistance, as well as every other form of fighting back.
I found a link to the study:
The values are from 1987-1992.
Here's one of the relevant portions:
Self-defense with firearms
*38% of the victims defending themselves with a firearm attacked
the offender, and the others threatened the offender with the
*A fifth of the victims defending themselves with a firearm
suffered an injury, compared to almost half of those who defended
themselves with weapons other than a firearm or who had no weapon.
Care should be used in interpreting these data because many aspects
of crimes--including victim and offender characteristics, crime
circumstances, and offender intent--contribute to the victims'