Having been under the hood of 208s and 210s with the M112 (V6) and the M113 (V6), as well as a 203 with the M112, I can unreservedly say that it is far, far easier to work on many things on the smaller engines in the same chassis.

A single example: the idler pulley on the M112 is literally a five-minute job on the M112 in the W210 chassis from tools out to being cleaned up -- and you don't even need to pull the belt if you are clever. The M113? It's closer to an hour and a whole lot more frustration.

The only exception I can think of is that the driver's side motor mount in the W210 chassis is easier on the M113, because on the M112 the A/C compressor has to be unbolted and moved out of the way to allow the MM to be passed through and out the bottom (and replaced via the same route).