I went with DeWalt and I don't really have any regrets. I had one of the really basic 12v drills from them for like 10+ years. It mostly rattled around my car's trunk during that time. I've purchased two additional batteries for it, one was shortly after I bought it, so I'd always have a charged battery on hand, the other to keep on the drill. When I needed to swap, I'd just take the dead battery into my home at the end of the day and charge it overnight, then dump it back in the car the next day.

I used it mainly for computer stuff, since I work in that industry.... Racking equipment in server racks, opening computers, etc. Rarely did I need to actually make holes or anything with it.... The third battery was purchased when the original battery that came with it, stopped working. The drill and two remaining batteries still work fine, though I don't really need/use them anymore.

I might "donate" it to a young relative someday, for now it collects dust in my basement.

When I replaced it, I got all 20v DeWalt everything. I bought a pack of tools that came with a couple of fairly basic battery chargers, a couple batteries, a hammer drill, impact driver, reciprocating saw, oscillating tool, a circular saw, and a portable light... It even came with a carry bag, which was promptly tossed in a corner and hasn't been touched since, except to kick it further into the corner.

After a short while of owning the house, we added a small (additional) set of batteries... I think 3 more? And picked up lawn equipment that's also 20v from DeWalt. A string trimmer (aka a "whipper snipper"), and a hedge trimmer. I feel like I'm forgetting something... Oh well.

The odd man out, so to speak, is the lawnmower, we ended up picking up a DeWalt mower, but it's 20v/60v, so it will take either pack. We had all 20v so we just stuck with that.

Then, I think last year? DeWalt released a snowblower, but it's 60v only. So we had to get specific batteries just for that. The 60v ones are compatible with the 20v tools, but the blower will only take the 60v packs, so we have two 60v packs for it (and the lawnmower, I suppose, since they can take advantage of the extra juice), and 20v packs for everything else.

Everything is cross compatible, with the one exception of the snowblower, so we're all set.

My experience with the 12v drill heavily biased me towards sticking with DeWalt.

I won't tell anyone to buy DeWalt or Milwaukee, or any other brand. You'll have to make that decision got yourself. I don't have any strong feelings about other brands because I simply don't have the experience with them to have an opinion.... Except Ryobi. Fuck Ryobi. My brother used Ryobi for a long time, and he had nothing good to say about them besides the fact that their tools are cheap. They're cheap in every way. You'll spend more trying to keep them working than you'll spend simply by buying better tools. Don't do it.