Would I gain a power or would I just be a member and attending all the luncheons?
i'd be a fairly mundane member of the avengers...
Or, perhaps, become one of the existing members (eg Wolverine, Cyclops, etc.)
You'd have a power (you can't be a member otherwise). The power would be on par with a typical x-man.
You get superpowers of some kind, typical of an Avenger
Where should this comment appear?
This pairing only
Whenever "Become a member of The Avengers" appears
Whenever "Become a member of the X-Men" appears