I understand that the M motor has an adequate amount of speed, and the XL motor is best known for its torque. But is the XL motor really faster than the M motor? Or is it the other way around? I am asking this question because I recently saw the L motor, and one reviewer said "It has the speed of the M motor but the torque of an XL motor." I am assuming this means that the M motor is faster...?
It delivers a maximum torque of 90,4 mNm (600 mA). Without load its rotation speed is around 220 rotations per minute.
It delivers a maximum torque of 45,4 mNm (450 mA). Without load its rotation speed is around 380 rotations per minute.
It delivers a maximum torque of 40 mNm (300 mA). Without load its rotation speed is around 380 rotations per minute.
Theoretically, in terms of power (speed • torque), the XL Motor is faster than the L Motor and M Motor. The reason being, you can gear up the XL Motor 2:1 and have the following output: running torque of ~7 N.cm & rotational speed of ~290 RPM. However, a small amount of these measures will be lost due to friction and decreased efficiency (by transferring drive through gears). Regardless, comparing these measures to the normal output of the M Motor — running torque of ~3.63 N.cm & rotational speed of ~275 RPM; and the L Motor: running torque of ~6.4 N.cm & rotational speed of ~272 RPM — and we have a clear winner, as far as running torque performance goes. Also, it is worth mentioning that the XL Motor has significantly higher efficiency than both the L Motor or the M Motor.
RPM measurements listed here are the loaded characteristics, not no-load. This is why the RPM numbers listed here are lower than what others have said.
Torque and speed measurements are according to http://www.philohome.com/motors/motorcomp.htm
It really depends on what you're going to be using it for. I'm in the middle of motorizing the fancy branded Lego Porsche and I was gonna use a couple of L Motors to drive the wheels and a servo to handle the steering, but after some research I found that because of all the gears going through the gear selection and drive-train, a powerful amount of torque is required and as Damon very correctly stated, the XL Motors are much more efficient in terms of performance. You might not be getting the same speed but you'll end up regretting buying the L motors due to their lack in torque. To solve this issue with my Porsche I just used a BuWizz controller instead of the old IR setup for more speed, flexibility and less weight as I don't need a receiver.
I bought an XL-Motor a couple of weeks ago, but when I saw a video of the M-Motor I knew it was faster. It seems to be that the XL-Motor can pull so much more due to the increase in the size of the whole motor but takes a lot more time to do a full 360-degree spin, and for the M-Motor it takes about less than a second to do a whole spin. If you want to buy a motor due to its speed but lack in torque, buy an M-Motor. If you want to have a stronger motor that won't get jammed easily, buy an XL-Motor.
If you already have an XL-Motor (or L-Motor) and you don't want to buy another (M or L) motor just increase the gear ratio. Take a huge gear wheel and get a small gear wheel and connect them to your build. Basically what is happening here is the big gear wheel is taking longer to make a whole 360 degrees spin and while it's trying to do that the small gear is going twice as fast as the big gear and therefore makes it go fast.