If you like effortless, easy speed, then the 500E is the one; if you like a more nimble, tossable ride then go with the C. But be aware that although a 500E feels slower than a C43, it isn't at all. I think it's just a bit more refined, so doesn't give the same visceral feel of speed. But if you look at the speedo, it's there
As a highway car, the 500E is unparalleled; but if you like to autocross, the C43 should spank a 500.
Both are fabulous cars; hope this helps!