From my experience, the salt water takes a faster toll on metals. The heater is likely to die sooner.
If the system is working, chemicals will be less. Things go wrong. The salt generator will need cleaning. It may die, need replacement, every 2-3 years. The control panel may die, new control board needed. The flow switch may die, new one needed (at $100 for the part).
Other than the salt system, everything else remains pretty much the same.
I backwash into the sewer, plastic pipes. I wonder if anyone here dumps the backwash from a salt pool on landscaping and what it does.