As of today, there is no question that bitcoin is best positioned to be the global currency.  First off, it's blockchain has been tested farr more so than any other coin and it's not even close.  People often look this over, but it's imporant to remember that until your blockchain is tested with billions and billions of dollars it's just conjecture to say that your chain is better and or more effecient (looking at your bitcoin cash).  Bitcoin will also become more and more effecient throuh further adoption of SegWit and the Lighting Network.