The truth is that there isn’t really much standardization of titles across agencies. Frankly, even within some agencies the titles aren’t well-aligned with responsibilities (or compensation).
My advice when it comes to titles generally is to focus on making them work for your own firm. Use titles that clearly delineate different responsibilities and come with designated salary bands. Be able to show team members a clear career progression available to them, and use the salary bands to enforce equitable compensation decisions.
When it comes to advertising externally for open jobs, titles are trickier because of the lack of standardization. An account coordinator in one agency may have minimal responsibilities and low pay whereas they might have a much stronger role and higher comp in another.
The title matters because it what gets someone to click on your job listing, but make sure that the description itself is as accurate as possible and conveys the level of responsibility (and pay) associated with it. That will help you weed out bad fits before either you or they waste any time.
Sometimes it may help to place two job listings even if you are seeking just one new hire. Different titles can attract different candidates — and you may even vary the descriptions a little bit if you are able to comp at a higher rate for one role versus another if you find the right person.
Finally, be careful about title inflation. This can cause issues whether it is done with new hires or internal promotions. It makes scaling more difficult and can actually hurt the ability of one of your team members to advance their own careers if they got a title that was larger than their actual role.