Unless you use some obscure browser, it is better to use your real user agent. If you keep your browser and operating system up to date, chances are it will be one of the most popular ones.

Your UA will correlate with other means of fingerprinting you making you more common. Being clever can make things worse.

For example, the most common UA is from an iPhone, but the most common screen width is 1920 pixel. If you decide to make your UA an iPhone with a 1920 pixel screen, then you will be easily identified.