The difference is in the thickness and the decorative pattern. An édredon is usually thicker although such blankets called "courtepointe" can be quite thick sometimes. An édredon comprises often enough no decorative patterns.

Édredons

Courtepointes

Quilts

As a quilt is usually "a warm bed covering made of padding enclosed between layers of fabric and kept in place by lines of stitching, typically applied in a decorative design" (ref.) and that it is not too thick, the best translation for "quilt" is "courtepointe".

The main difference between a courtepointe and an édredon is the filling material used, cotton or wool for the former, feather for the latter.

However, if you are looking for a translation that has a chance of be understood in France¹ by non specialists, I would recommend to avoid courtepointe.

A quick poll around me shows that nobody knows what this word is about.

Everybody actually call this kind of things a couvre-lit. If shown a quilt, most people would name it un couvre-lit patchwork or un couvre-lit en patchwork.

Édredon (comforter), unlike courtepointe, is a known word but tends to become out of fashion. Édredons were originally filled with eider feathers as its etymology shows: the word comes from the Danish ederdun (English: eiderdown = duvet d’eider). As I already stated, this is the main difference between édredons and courtepointes/couvre-lits patchwork.

On the other hand, younger people would probably simply call a quilt une couette (duvet), because couettes have almost completely supersede the former traditional bed upper layers drap/couverture/couvre-lit

¹_{That might be different in Canadian French}