I have both the DeWalt mid-torque (DCF894) and high-torque (DCF899), as well as the Milwaukee M12 stubby 3/8. They are the first ones I grab (before air tools), but I will admit their torque ratings are severely overstated.
The mid-torque ends up being my least used one by far now, which was actually the first one I got. You would think if you wanted a "do it all" type impact then the mid-torque would be it, but I find it severely lacking in power for most things. I drive a half-ton pickup, and I find for anything suspension related, or any larger bolts under the truck that are rusty, the mid-torque won't budge them.
So I usually go for the high-torque first thing now. It's big and heavy, but I also don't want to waste my time grabbing the mid-torque, finding it can't break the fastener loose, and then going back to the box for the big one. I don't have any experience with the new Atomic specifically, but it's rated at 450 ft-lbs, and the DCF894 that I have is rated at 600 ft-lbs, so I have a hard time believing the Atomic would be useful as a "do everything" tool. Looks more comparable to a replacement for my M12 stubby. Maybe people who don't live in the rust belt, or work on smaller cars, have better results with the mid-torque than I do.
The M12 stubby I grab if I'm doing brakes or something I know is either small fasteners, or in tight quarters. Milwaukee rates it at 250 ft-lbs, and their estimations seem to be closer to accurate than DeWalt's, although I still don't think it actually makes that much real-world power.
My advice to anyone just buying one impact for a variety of tasks would be to go for the high-torque DCF899, and then get a smaller one later for clearance issues. The DCF899 has three power settings, so you can always dial it back for lighter work. But you can't turn up the power on the smaller gun.