Questions of which device to buy are very subjective. As you see mustang has never used a Xiaomi and I've never used either, plus what I find important may not be the same for you and mustang may feel differently than either of us. You are better off checking reviews and watching comparison videos. This way you see what each offers and can focus on the things that are most important to you. In your case both of these devices are popular enough to have been compared to one another in more than one video on YouTube. I noticed around 10 just at a glance.
Compare Xiaomi 14 vs Google Pixel 9 with our phone comparison tool and get side-by-side specifications.
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IMHO, asking what people like about a device, or what features they use most, or even if they have any tips or tricks for a device, is going to be more telling.
Sorry it's probably not the answer you were looking for but I believe it'll serve you better in the long run. Best wishes and good luck.