Both are great systems. Makita x2 is a bit less powerful an less efficient than Flexvolt but you also have access to Makita's huge line of 18v tools. x2 requires 2 batteries but because they are just standard 18v batteries they won't add extra bulk when used with 18v tools. It also means you need to have at least 2 batteries charged because each x2 tool takes 2 batteries. DeWALT Flexvolt is the clear winner in terms of power. When under load it powers through just about anything a corded tool can. The battery is large and will add extra weight and bulk to a 20v tool. Except for the miter saws, all Flexvolt tools only require one battery. Flexvolt batteries work on 20v tools but 20v batteries will not work on Flexvolt tools. Another advantage to Flexvolt is all the Flexvolt tools are brushless. Makita may have the slight edge over Flexvolt but with wave 2 Flexvolt approaching we may see otherwise.