The shape of these mice is very similar. They are both tiny with the Viper Mini being slightly smaller. It is 2.3mm shorter at 118.3mm and 13.5mm thinner at 53.5mm. Both are almost identical in height and the shape of the curves almost the same too. SteelSeries and Razer advertise these mice as made for claw and fingertip grips only, which is very true. If you are a palm user I would suggest looking elsewhere. From my experience, I found neither mouse to be more comfortable than the other for either claw or fingertip grip, this is simply down to how similar they are.
The Rival 3 is just 77g while the Razer Viper Mini is just 61g. This is obviously a big selling point of the Viper Mini and is one of the few things that makes these mice significantly different. Both of these mice are very light and 16g less on the Viper Mini makes it feel much more agile and nicer to use at lower sensitivities. This alone is the reason I personally prefer the Viper Mini.
Both sensors have more than enough DPI range of up to 8500 DPI. They felt equally precise and responsive. The only difference is the lift off distance. It isn’t great on either mouse with the Viper Mini having of a lift of distance of 7 playing cars and Rival 3 tracking up to a height of 8 playing cards. While a difference of 1 playing cards seems almost negligible, I personally experienced noticeably more cursor jiggle on the Rival 3 while lifting and readjusting the mouse. This may have been due to the lighter weight on the Viper Mini causing me to naturally lift it up slightly higher.
The mouse clicks on both mice were good, taking the right amount of force to press and having the right travel distance. I cannot pick one or the other as having better primary mouse clicks so there is not really much to say about them.
The other buttons on the mice had a more distinct difference. Both mice have 6 programmable buttons: two primary mouse clicks, the scroll wheel click, a dpi changing button behind the scroll wheel and 2 side buttons. As I described in my review of the Rival 3, the thin, sharp buttons took way too much force to press in my opinion. I did somewhat get used to them but ultimately, they are a unquestionably inferior to the buttons on the Viper Mini.
Similar to the primary mouse clicks no scroll is really any better than the other. Both have a rubber feel and have a distinct scroll between each tick. If I had to pick a favourite, I prefer the scroll wheel on the SteelSeries Rival 3. I can’t really put my finger onto why, it just felt nicer to use in my opinion.
Lights and Software
The lighting on the Rival 3 is far superior, it has 3 RGB zones instead of just one with much more vibrant lights. You can create cool effects and it looks really good. On the other hand, the Razer Viper Mini has a single RGB zone and is quite plain and boring. You just have to consider the importance the lighting has to you since for most people the performance will be the most important thing. I will quickly mention the software; both were easy to use and I wouldn’t say either is better than the other. Both offer plenty of control and customisation and are easy to use.
I think it’s pretty evident from this video that I prefer the Razer Viper Mini. These mice are extremely similar and the only difference which affects performance is the weight. The lower weight gives the Viper Mini a clear edge over the Rival 3 for me. Obviously, you need to consider that the Viper Mini is $10 more. This isn’t a huge difference but depending on your budget, $30 could be the upper bound of what you are willing to spend. In which case, the Rival 3 is still a very good mouse and definitely worth its price tag. Palm users should look at other mice as neither of these mice are designed to suit that grip style. Claw and fingertip users will probably not mind which they are using since they are quite similar. The Rival 3 is obviously the better looking mouse due to its superior RGB so depending how much looks matter to you this could make a difference to you, however I think most people are more concerned about the performance than looks.