When I was younger and money was tighter, I needed a sawzall for a project and bought a DeWalt because they had a good price on a bundle. Many years later, my entire set is DeWalt because it was the convenient choice after I had two of their batteries. If I bought from scratch today I'd probably buy into Milwaukee, although the difference is small enough that I don't mind too much.
This is exactly why the “starter sets” are such good deals, they know if they get you you’re unlikely to change.
Milwaukee takes it a step further with the dual 12/18v chargers, because that would be a decision point that could make a switch - you could have all Dewalt 20V but nothing would stop you getting 12v Makita or whatever.
