Here is a test of cutting plasterboard (drywall) for electrical brackets manually with the gyprock saw, and with an M12 rotary tool and an M18 rotary tool. Here are the specs for both tools below:

Milwaukee C12RT Rotary Tool
Speed: 5,000 - 32,000rpm
Length: 240mm
Weight: 600g (without battery)
Collet: 0.8mm - 3.2mm

Milwaukee M18BCT Cut Out Rotary Tool
Speed: 28,000rpm
LED light: Yes
Length: 227mm
Weight: 840g (without battery)

There are a few factors to consider; manual cutting with over 20 years of experience versus the first try with Milwaukee tools and no experience whatsoever, as well as the non-work environment.

02:09 Gyprock saw (drywall saw) - could have completed the cut quicker than 37 seconds if the plasterboard was fixed as in the proper work conditions without it being flimsy. For the cordless tools, this is not an issue.

03:00 Milwaukee C12-RT - the screw cap fell off half way, but it's been edited as if it was a "seemless" cut. As it's our first time using this tool, the cut out could have been completed in at least 22 seconds where you can see it finishing the second screw hole reveal. Then you would get quicker as the experience builds on.

03:50 Milwaukee M18BCT - This tool is supposed to be the "main" tool for cutting out electrical brackets, but comparing its size and weight (especially with the batteries), we would prefer using the 12V version instead as it would be easier on the handling when you got to cut 70 to 100 holes per day. Similarly to the 12V version, this tool would have completed the cut in 22 seconds or less with experience. We let it go for just under 39 seconds (for "shits & giggles") as the screw holes werent revealed.

04:45 My thoughts. I gave the 12V tool the first place preference and chose the gyprock saw over the M18 tool because of the size, weight and the amount of dust it blows in front of the user.

06:45 Cutting plastic with M12 tool. Good for cutting out switches for lockers and lights in the dash, especially at low speed. It cuts very good and precise (if you mark it out first).

08:05 Cutting metal purlin with the M12 cut-off disc. At 09:36 I said 37000rpm (I think I'm getting blind).

10:05 Cutting more plasterboard

So... let's say you save 15 seconds per hole over the manual cutting, and you have 100 holes to cut in a day. That would equate to 25 minutes of saved time per day. As of April 2020, the C12RT costs $156AUD + battery. The M18BCT costs $219AUD + battery. Do you think it's worth it? Would you get one?