I agree with Nanonevol's thoughts, similar to my own. I'm guessing that the '79 is carburetted based on your location, but that was the year some spiders started to come with fuel injection, starting in California. By 1980, all spiders were fuel injected. So, if the '79 is fuel injection, that could be a deciding factor. I personally like carburetors, but many on this forum will disagree with me.
So, it's kind of a toss up. For me, I would probably lean very slightly towards the '79. One other factor would be the condition of the interior. While paint and mechanical stuff can be fixed, if there is a significant difference between the two cars in terms of seats, dash, center console, trim, etc, that would be a big factor in my mind as those items can be costly.
-Bryan