For impact wrenches - In the M18 line up (or m12) just concern yourself with the M18 fuel models.. they have different options for the models like 3/8 vs 1/2” drive, or friction/hog ring vs pin detent - but theres 3 main models in ascending torque ratings. The compact, the mid torque and the high torgue.
Obviously, the mid toque is the mid range, and the high torque is the biggest and most powerful.
The newest addition right now is in the m12 lineup, called the m12 stubby - which is actually a little more powerful than the smallest m18 impact, the m18 fuel compact.. just post what you wanna use it for and someone will tell you what model # you want.
Honestly dont even bother looking at anything non fuel. Its not what you want.
Ill go ahead and assume you want something bigger in 1/2” drive to start. You wanna either look at the mid torque in the 1/2” drive option (there is a 3/8” model too) or the high torque model in 1/2” (as opposed to 3/4” option for that model). Whatever you pick you want the friction ring model, not the pin detent. Does that help? Oh - and you dont need the One Key models.. One Key is an app that lets you customize the speed settings, and lock a tool on/off, or help locate a tool.. its honestly something 99% of people dont need.
1/2 high torque , friction ring -
https://www.milwaukeetool.com/Products/Power-Tools/Fastening/Impact-Wrenches/2767-22
1/2 mid torque, friction ring -
https://www.milwaukeetool.com/Products/Power-Tools/Fastening/Impact-Wrenches/2861-22
Also - the last 2 digits in the model numbers (xxxx-20 / xxxx-21 / xxxx-22) denote what comes with that tool. -20 is bare tool, -21 means charger & 1 battery, -22 means charger & 2 batteries. And i believe if there are letters on the end of the kit model #, it will denote what type of battery. Like ct will mean compact. Maybe there’s an hd (i dont even know) that will come with bigger batteries. There’s also 2 platform of m18 batteries now. Standard m18 that uses 18650 cells, and the newer heavy duty packs that have the newer cells, are they 21700 cells?
Yea ok - i can see how this can get confusing.
What most people will wind up doing is buy a drill and impact driver combo as a kit. That will get you your two most used tools, a charger and usually 2 batteries.. if you wanna add an impact wrench you can do a bare tool to start.
I think Home Depot is still running their holiday deals where you can get a free tool or free batteries with purchase of a combo kit right now..
When it comes to those, there are 3 tiers . In ascending order its M18 (brushed models), M18 Brushless (Brushless models with basically the same power as brushed) and M18 Fuel - (brushless, but more powerful). The impact drivers have a 4th option called the Surge, which is a Brushless oil pulse driver, which is just a different type of impact driver. There is only 1 model in m18, and one in m12 for the Surge.
The main thing to remember is if it says FUEL - its going to be the most powerful option for that specific type or size of tool. And YES - you will be paying extra for the 4 letter word.
Hopefully that makes things a little easier.
These tool companies are at the point that they really need an educational page to help people navigate all the options.
Also - the bigger the amp hour the battery will result in a slight increase in power.. so if you slap a 2.0 battery or a 9.0 battery in an impact - you can even hear the tool spinning faster. Its not life changing, but it exists. Generally though, the smaller packs are better to cut down on weight and size - and the bigger packs for runtime and best power. The 5.0 packs are about the best compromise you can get. At home I dont have any these newer 21700 batteries they recently started selling.. honestly it not even necessary as far as I’m concerned. The retail prices on batteries are crazy. Ebay is the best place to find genuine milwaukee packs, sometimes at even half of retail. For most of the core cordless tools, you dont need anything bigger than a 5.0.. i mean seriously, people were drooling a few years ago when a 5.0 was released as the biggest pack available, and now we’re up to 12.0’s.
The biggest i have at home are 9.0’s and they ONLY get used in my string trimmer and blower.