I’m a plumber that uses power tools all day every day. In my particular field, Milwaukee makes a lot of specialty tools that I enjoy, both in m12 and m18. I also have many dewalt 20 volt tools. I am, admittedly, easy on equipment and try my best to take care of my tools, and (knock on wood) i havent had one of either brand tear up in a long time. Ive had some m12 batteries eat **** lately but ive had them the longest of any platform and that’s to be expected.
I say all of this to say, if you’re not going to use these every day: go with m12 or dewalt 20 volt. Find the best deal at the current time and go with that platform. Dont sleep on m12, though. For a dyi or project around the house guy, its surprisingly strong, even the impact. (Btw, i use my 3 speed brushless Dewalt impact everyday and my 18 volt Milwaukee impact that i scored for 100 bucks with 2 batteries and a charger this summer literally never leaves the bag)
hope this helps