Of course, there is also the expression 'a job of work'.
I would suggest the word 'job' when it is used to describe one's profession or occupation is slightly informal, albeit very common.
'Occupation' would be more proper.
However, 'job' can also refer to a specific task undertaken as part of one's work. For example, tradesmen do 'jobs', and 'job order' (the request for a tradesman's services) is a formal business term used in the industry.
'Work' tends to refer to the actual physical activity of performing one's 'job', or 'occupation'. One can go to one's workplace, sit idly at one's desk, hiding from the manager, and do absolutely no work.