How does a modified Mustang spoiler compare to a Camry with spoiler?

[v8ismyheart]

So, my buddy’s got this Camry with a spoiler (don’t ask why), and we’re debating if my Mustang’s spoiler would actually improve aerodynamics compared to his. I know they’re totally different cars, but does anyone have experience with how spoilers actually change the car's handling at higher speeds? It’d be great to settle this with some real feedback so I can win the argument