My body is on the diminishing streak. Member since Dec 2011 8080 Points Moderator
It is one of those grey areas. Personally I would go by total play time per side, less than 10 minutes per side I would treat as a 12" EP, with the exception of "Mini-LP" being printed on the sleeve and/or label.
I agree also. If the release tends to focus on one song, then I lean towards maxi-single. If it's just a collection of tracks (especially with a separate title), then I think mini-LP. If I'm still undecided then I would go along with what The_Vinyl_Junkie says.