DC just converts your rtl to gatelevel. To reduce the number of cells in your gate level netlist you will have to play with constraints or how the design has been coded. In simple terms, larger number of gates in the gate level netlist, larger the area and power.
ICC on the other hand takes this netlist and lays it out. It adds buffers or inverters to compensate for the parasitics of wire lenght to meet the timing. If you don't have an optimized placement strategy, this means you will have more buffers and inverters leading to power and area increase.
Hope this helps.
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One more question? Are you a professional working for the a big MNC or are you going to one of the coaching classes?