The PEX4 unit has a lower cooling capacity and a higher power consumption than the PEX3 unit, but these may not be significant drawbacks for your data center. Your data center has a relatively low heat load of 4kW/rack, which can be easily handled by the PEX4 unit. Your data center also has generous ceiling clearance, which means you can use the existing CRAC units to supplement the cooling of the PEX4 unit. You may not need to add additional CRAC units, which can save you money and space.