I agree with above, officers don't fix anything as they aren't trained to. They manage (in theory) the engineering department and do most of the paper work, planning and admin behind the engineering. If you want to be hands on officer isn't the job for you. MESM rating you can go mechanical or electrical but the higher you get the more you are encouraged to cross qualify.
WESM don't have mechanical or electrical as far as I'm aware.
Time off . Most lads don't even get their annual leave entitlement at the moment so times are busy.
MESM can cover Mechanical (heavy stuff), Electrical and electronics.
WESM can cover mechanical (not the big stuff MESM do) Electrical and electronic.
At sea I had ME's asking me for help, and in turn I as a WE asked them for help.
both may have to look at software faults at times.
Hence a lot of basic theoretical training at Collingwood or Sultan will cover the same area's maybe even some of the same modules. the big difference will be specialisation at the end of training.
Plus MESM smell.