Mechanics if you’re doing physics, and intend to do physics, chemistry, medical sciences, geology, etc in university, or if you want to be a teacher in these fields.
Statistics if you’re going in social sciences like political science, psychology, sociology, anthropology, etc.
I hope I’m not too late ):
If you don’t know what you wan to do in the future, usually, the stereotype is that statistics is easier, because physical sciences are tough and abstract (thus difficult), but if you think that it’s relatively easy for you to understand the concepts in physics, then go ahead with mechanics.
that was a long sentence Personally, I think that since it’s all maths, both ask for the same amount of logic and effort.