So, which is it to be? I think people may think that advisor is more formal (even posher) in some ways, and it’s definitely used more in official documents and marketing-ese.
But in reality, this is another pair that means exactly the same. Adviser or advisor: just pick one!
What I would say (and what I always say), is be consistent. If you introduce a mortgage advisor on page 1, make sure they haven’t changed into a mortgage adviser by page 4!
Oh: but it’s always advisory (not advisery, which isn’t a word) when you’re talking about having the power to make recommendations (but not to enforce them, interestingly). “The panel is operating in an advisory capacity and cannot force the employees to wear baseball caps”.
I personally prefer advisor. What do you think?