How do they lock up, and how is that strain transmitted to the receiver? I would think that would be the crux of the question.
If the barrel contains all the pressure of the cartridge, except for the rearward both thrust, the difference in strength would then be the bolt lockup. It would seem logical to assume similar strength in the barrels of the two different guns, if they are similar diameters (which I don't know).
So.... the M94 and it's variants have twin vertical lugs at the rear of the receiver. Could be (my speculation!) why Winchester had to beef up the receiver walls to contain increased bolt thrust. How does the Marlin lock up though?
The solid top on the Marlin receiver should in fact help keep the receiver more rigid, but whether this is a factor would depend on what part of the gun bears the brunt of the bolt thrust. Or another way to look at it would be that the Malin could have thinner receiver walls than the Winchester, and still be as rigid.
OK who knows how a Marlin works..... the only Marlin that I have is a M39 (.22), so that's probably not a useful comparison.