The cast start as dating couples in CD and friend couples in L&J.
They go on dates with the others, change their dates too.
In CD, couples try to find if they r still in love with their partners or they want to start a new relationship with the other. CD is a show of couples, hence it's realistic and portray real-life problems between them, Whereas in L&J, they try to find love between friends or other partners. This is more of crush and lust, in my opinion.