I'm like shipwreck...I prefer a high and medium mode and like the ability to switch between the 2 just by twisting the head. I prefer this type of UI much more than having to click multiple times, even if the light has memory.
For the M20s, keep in mind that it has visible PWM at the low and medium modes. The standard M20 doesn't. I prefered the M20s over the M20 until I found out about the visible (pretty low frequency, about 100Hz I think) switching frequency.
Other similar lights in this class are the Jetbeam RRT-2 and Dereelight CL1H V4...both use XPG R5s.
In my research for a replacement to the T20, including the RRT-2 and the CL1H V4, I understood the PWM flicker was a possibility, so I asked other owners of their experience with feedback ranging from little to no flicker. So I went ahead and placed an order knowing I could get a free exchange for the M20 standard. But I have zero flicker issues on any mode, which is nice.
As for changing modes, having the T20 and the Maelstrom G5 right here to compare with the M20S side by side, in my exerience, I can switch modes a bit faster by clicking the side switch (despite having to run through the low and strobe modes), than I can by turning the bezel on either of the other two and
I can do it one-handed.
Additionally, the M20S's 320 lumen rating must be OTF compared to the T20's 300 OTF rating, because that's what my eyes would suggest is the brightness difference in favor of the M20S.
Plus the bonus feature I really appreciate with the M20S is that it provides a measure of safety assurance for my wife and kids, none of whom are flashoholics or even technically adept, in that all of them can reach for the light, feel for the side switch in order to activate the strobe without having to worry about pressing the tactical switch first. Like any form of self defense, it takes a little practice, but I showed them how to position the light in their hand using the pocket clip as a reference point and for added grip, in order to find the side switch quickly. It works, as they are able to accomplish this with very little effort and that gives me peace of mind.
As much as I really liked my T20 and the ability to switch out drop-ins, in real world practice, I realized that when I had another drop-in available, I would have preferred to purchase a second or third T20 for the different modules. But the T20's Q4 neutral was not of great interest to me vs. the cooler tint of the XPG-R5 and the Maelstrom G5 blows away the T20's R2 drop-in, so there's no need for that one. Factor in no last mode memory, which meant
waking up my wife in the middle of the night if I wanted to use the T20 vs. having a moonlight mode already set on the M20S or M20 for those that have that model. I don't like to get yelled at in the middle of the night if I can avoid it.
Last, the M20S has the same accessories kit as the ET T20C2MKII, but also has a cool carrying case (albeit unnecessary), with a better battery carrier for use with CR123s. Olight also offers colored diffuser filters as well, but you don't need to take the time to remove the tactical bezel ring to screw on a color filter as with the T20. Finally, the T20's pocket clip is useless as it comes off very easily whereas the M20S's is solidly attached.
The bottom line is, "to each his own", but for me the M20S is far superior to the T20 in every way that I need for a
general purpose light. The fact that it was designed with LEO's in mind, means I can also mount the M20S on my rifles if desired, like the T20, which is also nice.
Disclaimer: This layman's review is provided based on my experience alone, yours may be different, so see your doctor before purchasing this light. Oh come on, that's a little funny!
John