I just saw both of these used for (and translated as) “he/she was talking about” as in “the X that he was talking about”.
I know that hanasu normally means more a back and forth conversation where iu more refers to a single thing that someone says. These seemed to be used pretty interchangeably in this case though.
Are there any important differences, or can these largely be used the same way when used as a past progressive?
Maybe seeing the full sentences you’re talking about could help shed some light on it.
I think that 話す is not usually used to indicate a specific thing that somebody said. Since 話 means “story” I’m guessing that 話す could probably be translated in some contexts to “to tell a story” (whether fact or fiction).
言う is basically “open your mouth and let words come out” whereas 話す is “express something with a long and coherent explanation”. In group settings, 言う implies a fairly one-sided thing - one person doing all the talking - whereas 話す implies a more mutual thing - a discussion.
I’d reckon I’d translate that as “I think this is a different restaurant than the one she was telling me about”.