It's surprisingly hard (at least for me, perhaps I'm looking wrong :p) to find general comparisons comparing the brands for overall usefulness. You'll find stuff comparing their drills, or something specific, but not everything overall. Which seems much more important, as (as has been mentioned in these comments) the batteries really lock you into one brand.
I mean, you can't really measure the brand overall like i think you're talking about.
Cause every brands gonna have great tools, mediocre tools, and bad tools. Though I think we can universally agree dewalt is overpriced and exploitative lol.
I believe you can buy batter adapters that let you run, say, Milwaukee off Dewalt batteries. Most of them are just direct metal adapters, no circuitry or anything. You could even 3d print and make your own if you were inclined.
So if you are deep in one battery ecosystem, you should be able to still run a tool of another brand.. as long as you are matching voltages (don't run a 18-20v tool off a 40v battery, for instance)
What are the magic search terms for these things? I went searching for such to adapt my porter cable batteries to craftsman (since they're all Stanley black and decker) but I didn't find anything. Looked on thingiverse too. I'm ready to print up the adapters! This lock in sucks!
Be the change you want to see in the world. Start up a spreadsheet or database and start looking to see if there's a way for others to add to it and view it, like a Google Sheets or a non-Google equivalent.
Can't really compare cordless drills to circular saws, that's apples and oranges. If you're going to buy into a tool line (the only real reason is to avoid having to purchase multiple chargers and batteries, those are expensive) then pick the one that has the best tool(s) that you use the most often.