As with any measure or score for online / digital space, you must fully understand exactly what you are comparing to make sure you make meaningful comparisons.
This is why you will not normally try to compare two different types of evaluation systems because they are designed for different purposes. In addition, it is only interesting to compare the ratings given for this type of website rather than looking at the general / general notes.
I think the best thing to do would be to look at the average breakdown of the SUS or WAMMI scores for specific aspects of usability for the comparison you are trying to make, and look at the correlation between these measures rather than the two rating systems. in general.
In the end, I guess it depends on the purpose of your questions, but I think the best solution for you will be to apply both measures to the website you want to evaluate and see if there is a good match between the two or not. .