Reverse osmosis forces water through a semi-permeable membrane. This removes dissolves contaminants that can't be removed by even the smallest filters. Reverse osmosis is usually combined with at least one carbon filter to remove organic contaminants such as chemicals, taste, odor, and color. There are a few primary components to the system that vary including the membrane, storage tank, faucet, and type of sumps used. Higher quality membranes remove more contaminants and last longer.
New membranes have a limited shelf life.
Old style faucets have lead containing materials that can leach into the drinking water. Low quality sumps can crack and leak causing thousands of dollars in water damage to your home. Eco Home Products aren't the cheapest systems on the market, but use the highest quality components as described above. Carbon filters are similar to a mountain spring water, reverse osmosis is a purified water similar to distilled. Carbon filters do not remove dissolved minerals which impart a unique taste on the water.