I use a mix of Milwaukee M12 and M18, and have zero desire to switch.
The Makita 40v and Dewalt 60v rear handle saws smoke the Milwaukee rear handle, but most of my serious Skilsaw use is still better served by my old Mag77 corded saw with an 8 1/4" finish blade (post, beam, beam wraps, etc) . My 6 1/2" sidewinder is fine for everything else. I rarely do production framing that is heavy skilsaw use anymore.
I've got a few guys that use Makita, and their drills and impacts vary a bunch. The top end stuff is great (probably as good as Milwaukee) but the lower price stuff is very disappointing.
There's a couple of guys with DeWalt 20v stuff, and it generally runs pretty well. I don't think you can actually really go wrong with any of the big 3 these days.
I do like that I can charge both my M18 and M12 batteries on the same chargers (and stack a second battery in the charger to charge when the first one's done).
Obviously they are king of the hill for HVAC, plumbing, electrical which doesn't do much for me but Milwaukee also seems to have more automotive oriented stuff than Makita or DeWalt, which I do use and plan to get more of.
I have a string trimmer which I like because I can use my existing batteries with it (actually love that little trimmer), but if I were going to go all-in on outdoor battery stuff I probably wouldn't do Milwaukee. If I were getting a mower I'd want something higher voltage (maybe ego? Stihl? haven't really looked into them) and then get the saws/trimmer/blower that uses that battery platform. Super high continuous amperage draw like a mower puts on an 18v battery leads to imbalance between cells in the battery and shorter life. Higher voltage/lower amperage discharge (and especially balanced charging) helps a ton with battery health as I understand it.