A lot of this will come down to the surface area mentioned earlier on in the thread. I once put three types in one tank just out of curiosity, I was testing with multiple DC's to see the co2 in different areas, to be fair the blau type you have there for me wasn't meant to stick on the side of the tank it hung on the glass with the fluid side on the outside of the aquarium which made the colour easier to read. The down side of this was it was also closer to the water surface where co2 content was higher (gas rises out) I also had a large DC and a nano one in the same style as the other one you have there.
At the end of the test I put them beside each other to see if they would give the same readings and waited until the following evening so they both had plenty of time to level up. What I found was the nano one was slower to react to change, the more surface area of fluid per volume you can expose to the air the quicker it will react. This made the nano one not much use tbh. Injecting gas has a relatively small window if you want to do it properly, you are looking for optimum saturation when lights come on and once lights come on plants start using up that co2. You also have to allow for an hour or two lag, the DC will tell you roughly what the levels were a couple of hours ago. Ideally you want your DC to be as close to real time as possible, without knowing the lag time if the DC is slow to react you may be looking at 4 hours until you get a reading that was somewhere from around lights on at which point your lights are going off shortly.
With a design like the Blau with very little surface area exposed you might not get a real reading until your lights are going out. Measuring using DC's has never been an exact science that people can obsess over. Measuring PH drops in real time is marginally a better option but when you start doing water checks every half an hour you hit the point where you aren't looking at the lovely fish and plants any more which is why I no longer inject co2
I maybe will again in the future though if I ever find the time.
It isn't what you wanted to hear I know as these things do look cool, I have some myself but they are more aesthetic than practical IMO