The Mech Eng programs focus on key mechanical industries such as hydraulics, mechanical design and development, and production line design/development/management.
Whereas, Mechatronics combines mechanical eng concepts with electrical and software eng concepts. It focuses on the Automation, Robotics, and Controls industries. Mecahtronics is a multi-disciplinary program/field, meaning, you are taught bits and pieces from mech, electrical, and software eng. Because of its multi-disciplinary nature, there is more course-workd and less time to learn and absorb it all well.
It is important to look at your natural inclinations and your interests before jumping into a program. If you have always been into robotics and have some experience with it, then mechatronics is a good choice for you. If you have always been into cars and/or have experience working with your car as a hobby, then go the Mech Eng route.
If you want more info on the types of work Mechatroincs Engineers do, contact your local university and ask someone or you can attend info session at the university. You can always google something like 'mechatronics jobs' or 'mechatronics universities.' And inquire from there.
When you are doing something you enjoy, working hard is never a problem. Always remember that.
I hope this answers your question.