American Tower (NYSE: AMT) and Crown Castle (NYSE: CCI) have a lot in common. American Tower now has about 223,000 sites in over two dozen countries around the world, including more than 43,000 towers and distributed antenna systems in the U.S. The Boston-based trust is also making its mark in data centers, having purchased fellow REIT CoreSite Realty and its dozens of facilities in a $10 billion deal announced last November. Houston-based Crown Castle has about 43,000 cell towers of its own in the U.S. It also has a fast-growing collection of about 115,000 cell nodes and 85,000 miles of fiber cable that are a big focus of its efforts to facilitate and capitalize on the 5G rollout.