but they are so different & one cannot really say that the CLS is a coupe with 5 doors. coupe style maybe. its a huge barge!
yes, the E coupe has the C class platform, but it is built to the E class spec, so comparable to E classes, rather than Cs.
The CLS is arguably a little above an e class so may be slightly more refined, but not quite got the handling of the smaller car.
Ultimately they are for different jobs: the e is a coupe; the CLS is a saloon but with a bit more style.
on a tangent; the CLS brake is based on E estate, & whilst more stylish(?) it is far less versatile & spacious than the E