I got tired of having too many types of batteries and chargers in the garage -- mostly stuff for wrenching on my cars -- drills, grinders, sawzall, circular saw, impacts, etc. Ditched all my non-compatible stuff and went exclusively to Milwaukee M18. It was painful at first, but really simplified things.
I was loyal to M18 until a few months ago, when I bought an M12 3/8" compact impact driver. It was worth it -- that sucker has some serious oomph.
I want to buy a battery powered chainsaw and now I have a conundrum -- do I buy the Stihl, so all my user saws match? Or go with the Milwaukee M18 saw so all my battery powered stuff matches?