I chose it after some research and because I had a good experience with the larger headphones from the same company (WH-1000XM4) for listening to music and phone calls at work where open music is not allowed.
After >200 hours of use, I can say that I am not going back to the large headphones because the fit of the small ones is perfect (my ears do not get hot like they do with the large ones), they provide very good external sound isolation (not at the same level but close to the large ones), they have excellent call quality (just like the large ones), and satisfactory battery life (at least 5-6 hours of continuous use, clearly shorter than the large ones which reach 25-28 hours), but at least they charge quite quickly through their case, so during a quick lunch break, they start fully charged for another 5-6 hours!
There is the option to choose the size of the ear tips (3 different sizes come in the package, I think) and the control from the mobile app to see if they fit correctly for complete sound isolation. They stay securely in the ear without the risk of falling during normal walking and various movements I make at work. With simple light taps on the headphones, you can perform various functions without using the phone, such as changing songs, answering phone calls, adjusting volume, and selecting the level of sound isolation (full or partial), which I find extremely useful.
The mobile app is important because you can set the desired equalizer, assign new functions to the taps, check the battery level of the headphones and the case, as well as update the software. Overall, it is hassle-free in an IOS environment.
As for the connection of the headphones to the phone, it is hassle-free 19 out of 20 times. Sometimes one of them may not connect, and then you just need to take them out and put them back in the case and try again. The connection of the headphones to the app works most of the time (16/20), but even if they do not "appear" in the app, they still function with all their features.
In summary, the headphones are of premium sound quality, and in the end, I believe they are worth the money and I would recommend them without hesitation! I definitely do not see myself going back to the large headphones because you just feel a constant weight on your head and they heat up your ears causing discomfort.
Rating for the WF-1000XM5:
10/10 for comfort
9/10 for functionality/ease of use