We would have to know the rotating mass and stroke length of each reciprocating assembly but if I had to venture a guess I am pretty sure the rod & pistons of the m3 will endure more force @ redline due to their higher acceleration.
Displacement has a little to do with it but it's mainly the RPM, the displacement plays into how massive each reciprocating assembly is (bore although the materials & manufacturing techniques play a larger role) and how fast the piston is being accelerated and decelerated each revolution.
All the info you could ever want right here:
http://www.epi-eng.com/piston_engine...celeration.htm
You will just have a tough time getting values for some of the dimensions like rod length & piston mass.