This is a short review-ish on the M220 & M221 as I’ve been using them for around 2 years now and found them to be nice, albeit with an asterisk* as while they do work, it isn’t really without any caveats and drawbacks. These issues are specific to the ones that I own to which other people might experience different set of issues or even none (lucky).
Going over the issues first, the M220 functions fine-ish for the most part except for the fact that if you leave it idling for like 5 minutes then the mouse wouldn’t function, requiring you to press a button or turn the mouse on & off to get it back working again. This is plain annoying especially if you’re someone like me that doesn’t really use the mouse too much and thus would often have it idling, resulting in you constantly having to fiddle with the mouse just to get it back working. Meanwhile for the M221, the mouse feels a lot more fragile compared to M220, as a result the “shell” of the mouse has crackled for me, resulted with a lot of unregistered clicks if you’re not clicking it properly. This is also plenty annoying and is the main reason as to why I mostly stick with the M220.
Despite these issues, I’d still recommend getting either the M220 or the M221 as a work mouse if you’re looking for one. For once, they are plenty cheap as each of them will only set you back for about $10-20 (depending on where you get it from) and at that price point you’d be getting a small-sized mouse with clicks that are silent. I doubt any other cheap mouse in the market can compete with the silent clicking that these mice produced. The silent clicks also indirectly make the clicking feel effortless and just nice in general in a way that I can’t really describe. Even then, one of the thing that might throw people off from using it is the fact that it runs on batteries (AA to be exact) since on one hand it’s nice not having to charge your mouse, but on the other hand having to constantly be buying and having extra batteries at hand or else you just wouldn’t have a mouse is not only a money-burner, but is also a general annoyance. While I do get that some people may prefer the fact that you can just pop a battery in and out to get it to work, I personally am starting to grow tired of it.
If you’re thinking of using these mice for light gaming, then I honestly have no idea how well it plays in that regard as I don’t really game a ton. I assume that it’d probably work just fine, but the small size of the mouse might feel bit uncomfortable if you’re someone that prefers a bigger mouse. An additional mixed note that I’d like to add is the fact that these mice are ambidextrous instead of being right or left-handed biased. I’m personally not a fan of ambidextrous mice, but in this case it’s kinda just ok where I can use the mouse with my left or right hand and can mostly achieve the same result. In a way they are probably the “best” left-handed mice that I own for now which isn’t to say that they are great, but moreso that a lot of ambi mice are just “bad”.This short section will be going over the differences as I found that there aren't much resources online in regard to comparing the differences between the two. In essence, I feel that the main difference would be that the M220 have buttons that are bit harder to press and feels more “rigid” compared to M221. The M220 also has bit of a different-ish shape where the M221 would go a lot more downwards compared to the M220. Ultimately, if you want your click to have bit more effort being put into it then get a M220, if you want your clicks to be even more effortless at a cost of possibly even worse QC then get a M221.
In conclusion, even with said QC issues I’d still recommend people to get either the M220 or the M221 if they are seeking a work mouse as they just feel that they are comfortable using. I just would probably pray that you don’t end up getting a very shoddy one I suppose.