The first difference is that the EF Series, and the PBS400 for that matter, are carbon block rather than Everpure's traditional and proprietary 'Precoat'. This means they can handle a higher flow rate. A traditional Everpure precoat filter (H300, H104, H54) is rated for a flow rate of 1/2 gallon per minute.  The EF series are rated for 2.2 gallons per minute. This is why they are referred to as 'full flow'The second difference is that these carbon block filters can be installed directly to an existing faucet; they do not require a stand-alone dedicated faucet. This means you can install it right onto the cold water line of your existing kitchen faucet and filter lots of water, for cooking, drinking, washing vegetables, etc. The one similarity is that all these filter cartridges are interchangeable and fit into the same head.