The reasons no one has bothered to discuss the image comparison you want is precisely the reasons they've listed for why those comparisons would be difficult at best and meaningless for the most part.

Also, I would prefer for you to spell out specific differences you think you see.

However, in the spirit of looking for comparisons and proving a different opinion prior to you revealing yours, I've stared at the region in question. Cross mapping the two images is difficult because the gridlines are only on one image, and because of the stretched angle they don't overlap, but I've managed to see what compares to region C7. Here is what I see:

First locate the region in question on both images. On the second image, it is located above the gash, centered in the double groove between the fractured/cratered left and the tiers of the middle. If I could describe the shape of the gash, I might suggest it resembles a submarine, with the conning tower in the middle including a large observation platform, and the nose projecting forward to the spiderweb crater on the left. Thus the C7 zone is above the middle of the nose.

Just to the right you can see a bumpy ridge line and a smooth valley with the shape of a boot, toes pointed right, kinda like Louisiana and above it Arkansas. The "Texas @ Oklahoma border" stretches up the left of the valley, which runs right along the edge of the right gridline.

Looking at the Viking mosaic, I can see the jagged ridgeline that runs down the right of that valley, and the shadowy shape of the left ridgeline. I can't really make out the boot shape very well, but I see the feature of the connected rough valley off the toe.

Now that I've located the region in question, I see in the Viking image what looks like a dark ridgeline running west across the region. Okay. What is in the MOC image? At first glance it looks smooth with a small crater at the lower middle. Closer investigation, however, suggests there is some texturing from highland ground to the south of that zone and lower elevation to the north. One can in fact see a hint of a slopeline between the two regions that matches fairly well with the ridgeline in the Viking image. The crater itself is not specifically visible in the Viking image, but the dark and light colorations and low resolution make comparison too difficult.

In summary, there is nothing distinctly different between those two images in the region in question.