Should I buy new batteries or a whole new tool system?

I have a DeWalt 20V XR drill and impact combo that I have been using for over 10 years, they still work great and are my daily tools. I recently lost a battery and I am down to one 2ah 20V battery to share between both. I don't do a ton of hard work with these tools, maybe 20-30 3/4 fasteners a day and 5-6 masonry tapcons that need drilling first. Switching them back and fourth really sucks but I am managing so far.

I have recently been interested in the Milwaukee subcompact M12 impact gun too. I am thinking I'd use this for driving fasteners and use my DeWalt with the one battery for the hammer drill.

I wonder though, should I shell out the money to buy new batteries for my DeWalt to get them back up and running or just buy the new Milwaukee subcompact drill/driver as it comes with 2 batteries?

Does anyone have any real world experience with the Milwaukee M12? Or longevity of the DeWalt XR tools? Last thing I want to do is buy $300 batteries and my DeWalt tools crap out.