There is definitely a difference looking at the two you can see it, I think I'm going to get some of the Chevy engine red when I get a chance. I was a painter for quite a while and believe me I understand about the different shades and ultimately like you said it's up to me. I want it close but I don't need it exact which is why I will use the Chevy engine red.
I get it on the Petty colors, that Petty Grand Prix I started was done with what Testors called Petty blue t the time (early 90's) and isn't to bad but the Petty Red that I bought the same time wasn't even close it was more like a florescent orange and probably the reason I lost interest in the kit....
You can definitely see a difference there, it is amazing how different colors are from photos and in real life