...that there would be a clear comparison between a diecast and resin version of the same car by the same manufacturer and both are in yout personal 'must have' category.
For me it finally happened with the Minichamps 917/10. I liked the 'L&M' diecast version released several years ago (though at the time I was disappointed a Follmer version was released instead of Mark Donohue) but the RC Cola version was the one I really wanted since it was the car featured in my Aurora AFX Slot Car set.

So now both are available and photographing the two side by side, my impressions include:
The resin version looks 'cleaner' without the inconvenience of shut lines. The white paint is brighter on the resin version.
The diecast version looks more authentic in my opinion, not only because of the color and the opening parts, but because the aluminum side pods actually shine, and even details like the tires are replicated with more care. From three feet away in a cabinet, will I really see that difference? Maybe not. I'm glad to have the RC version for sure, even if it cost twice as much and the quality (my opinion) isn't half as good.
Your opinion may vary...