I have been comparing instrumented test results between the two publications for more time than I will admit.
I think the weight is a wash. My reference to it was more of a "wow, it was SO much quicker and look, it was even heavier."
All of the variables you listed do play some part in generating different results when testing "like vs like." But the vast majority of the time the results are very close. Maybe a few tenths/mph difference (half a second max). This is by far and away the largest difference I can recall. Its as if MT tested a 2019 and C&D tested a 2020.