SRAM is made using 6T and hence occupies more area and is more expensive. It's faster in operation compared to DRAM. SRAM is volatile. DRAM is made using one transistor and one capacitor. Hence the area is minimal and the cost is less too. But as the information is stored as charge on the capacitor, leakage is more in case of DRAM and the DRAM cells have to be constantly refreshed to hold the data, this refresh is not required in case of SRAM. The DRAMs are cheaper and are generally used in HDDs.