I've been slowly adding cordless tools to my collection and they've been great. It started when I found a DeWalt 20v max (which is actually 18v, like all the others) drill with 2 batteries at our local garbage dump. Yep, that's right.. at the dump.
I liked it so much that I ended up purchasing a grinder, circular saw and a handful of 4Ah batteries. They now have 5Ah batteries.. very tempting.
If I was starting with nothing I may have considered Makita or other brands, but having a free DeWalt drill kept me with DeWalt.
I'll tell ya, that grinder is great. We have a bush lot with no electricity run to it and with a couple batteries and a cut-off disc I can blast through plenty of steel. The torque on that thing is better than my previous plug-in grinder.
I also picked up a car charger so I can easily charge the batteries inside the bus (with the solar panels) or in the car while driving. The 4Ah batteries fully charge within 30-45 minutes so I can keep a mostly steady work flow, sometimes with a 10 minute break in between.
It's certainly an investment, though. If you already have an assortment of power tools and don't expect to get LOTS of use out of new ones, then just get a generator. Way easier. A generator is also 1000% (approximately) better than running the bus engine to charge batteries or run an inverter.