I am one of the few smokers who does not care for Chelsea Morning. For some reason it was very finicky about the particular pipe that was used and it just came out tasting "Meh" to me. But I'm in minority. Most people love it.
Quiet Nights on the other hand, I have pounds of the stuff put away and really enjoy it with a little age on it. But even fresh, I love it. Probably my favorite English/Balkan blend out there.
I don't find the two all that similar, to be honest. CM has a touch of Latakia in it, but its flavor is dominated by the Virginias and the Orientals.
QN, on the other hand, has a very substantial amount of Latakia. So the flavor is deeper, richer and more full in my opinion. Plus it is based mostly on Red Virginias and it is pressed into flakes. So the heat and the pressure of the pressing has changed the overall flavor to something almost stoved.
If you're looking for "sweeter, more peppery", then CM might be where you want to start, but you owe it yourself to at least try QN. It is a great blend.
Another choice might be Westminster. A great "all day" English/Balkan with a good measure of Oriental leaf, but no Perique. It is sweet and spicy (not pepper, per se; but more cooking spices) with a enough smoky Latakia to give it some depth and earthiness.
Hope the search works out for you!