I recently had to break out the trusted AP Stylebook for grey vs. gray (gray is the preferred, just so you know. Grey is ok for greyhound, but that’s it).
While I was there looked up adviser vs. advisor because spell check kept telling me advisor was wrong. Turns out, spell check is right by AP Style. But both are widely accepted as this post from Purdue points out.
Like in so many -er and -or words, as long as you are consistent, it doesn’t really matter.