Thought I'd find the
oldest possible thread to revive that I could today

.
I'd found this thread among the more valuable/constructive, as I was starting to casually research cordless impact wrenches a couple months ago. Read through it again today, Thought I'd add to it...
Came across this Shop Tool Review write-up (bit.ly/2O3OeDajTp) from late '17, so it's still fairly current. Their review of 9 cordless impact wrenches was very well done in my opinion. Very constructive and takes perhaps 20 minutes to review/contemplate. By the half-way point you start to get a feel for how things are going to shake out.
The short take, there are two distant last place finishers; ~5 strong mid-pack competitors in the middle; and, by a leap, one clear winner using their metrics. I want to get a model that can use my existing battery system. However what I found left such a strong impact, I expect this weekend I'm going to be adding another color charger to my garage.
If you think you're going to get one, I recommend sitting down and enjoying the read.