Hi Zak,
I believe the build quality of the cars were very much the same.
I owned and restored a 63 220SE Coupe, 61 220SE Cabrio and 65 230SL in the late 80's and early 90's. I took them apart and looked and scratched in every nook and cranny. The Coupe was restored to be our family car and the Cabrio and Pagoda became my daily drivers up to about 2000.
Although the 111/220SE cars had earlier model engines and fuel injection systems, the cars were very much the same.
You would probably find the Coupe and Cabrio seats were sturdier because of continious accesss to the rear seats, whereas the Pagoda was not really meant to be a 2+2.
Nearly 20 years later and I still have sellers remorse and pine for my 111/113 babies.
Regards
Chris