"Our jobs are the same, why are the salaries not the same?"
工资and薪水are pretty much interchangeable. In mainland China, 工资is the most common term for salary while 薪水is a little bit more formal. This might be different in Taiwan.
Thanks for the response. I did indeed learn the term "薪水" in Taiwan.
To clarify and dig a little deeper, is there any difference in the generality of the terms, to your mind?
In English, "salary" has a narrower meaning than "pay". They overlap in usage, but we don't apply the term "salary" to hourly wages; we use it to describe a fixed amount of pay over a longer period, usually a month or a year (1, 2). I don't get the sense that this limitation applies to "工资", but I still wonder whether it applies to "薪水".
Anyway, if "工资" is more general in meaning than "salary", then perhaps "pay" or "wage(s)" (both of which are broader in meaning than "salary") would be a better introduction to the Chinese here. There's an even stronger rationale to use these latter terms in the back translation.
(In a sense the concept of "wage(s)" can include the idea of "salary", though "wage(s)" often refers to hourly, daily, or weekly pay. "Pay" is the most general term of the three.)
Edit: Downvoters, consider being more helpful by providing a reference or a rationale.
Keep in mind that typically in China, employees are paid monthly SALARIES rather than hourly WAGES. This gives the boss the advantage of not having to pay overtime. Work hours are very fluid in this environment, and unfortunately, the tendency seems to be to overwork the workers.