My thoughts are really focused more on comparing current models (new 911's and 718's) as it's difficult to compare older models of cars with the current offerings. Like watches, some people love a brand new watch while others love the nostalgia of something old. While the new Porsche models are on paper all better sports cars than their predecessors, both are fun for different reasons.
Don't forget the Alpine isn't available in much of the world, unlike the Porsche (though, I'm not sure I'd pick it even if it was).