All four of the sample images were shot under four different lighting scenarios. Even the two shot under daylight will be different due to the influence of all of the green vegetation in the first shot.
The fact that you used a very different film for the first two shot with the Contax than you used to shoot the second two with your Yashica makes it even harder to compare the two results. If you, presumably, used two different lenses that could also affect the color and contrast of the images.
To really compare two different films you need to shoot the same scene under the same lighting conditions using the same lens and have them processed and scanned/printed at the same time by the exact same processing.
In general, it appears the first two images shot with the Contex are a bit brighter than the other two shot with the Yashica, so the meter of the Contax might not be as sensitive as the meter in the Yashica. Or it might be that the roll from the Contax was developed brighter. Whatever the reason, brightening the image also tends to reduce contrast which compounds the fact that Superia is more contrasty than Portra to begin with.
The second image appears to have been shot under some fairly limited spectrum fluorescent lighting, which tends to look green when used with daylight balanced film if not corrected with a proper filter when shooting.