The biggest difference between the 116 and later 126 lies in the SRS - ABS, airbags and seatbelts that tighten under sudden deceleration. New engines and aerodynamics resulted in the 126s being more fuel efficient despite huge increases in engine power output. The big difference to me is that the ACC system is greatly improved in the 126. Manual AC in either car is still my preference. I don't think there's much difference in cabin size. The foam seat padding in later 126s lasts longer than the horsehair padding in 116s and early 126s.

Sixto
95 S420
87 300SDL
83 300SD
78 450SEL ... sold