They are quite different, in my mind both pretty good.
CDS is more glitzy in places, expensive, lively, noisy, cosmopolitan. Costa Calida is better priced, more Spanish, relaxed, better beaches, seasonal and marginally more friendly.
I reckon CDS is a place that's well suited to visit as a holiday destination, but Costa Calida might be better to live for longer periods. Of course it really depends on the individual.