My two cents
I'm biased as fuck. Obviously, I find that Service Design is a super interesting career choice. Service Design is my passion, and I believe you can live that passion in your job and outside of it. But to come back to the question, should you choose UX or Service Design? Frankly, it doesn't really matter because:
Most of us will change careers a few times, so it's all just a starting point.
Both fields are much closer than what many believe. UX and Service Design are like cousins. In how it's practised today in many companies, UX might focus more on the digital aspects where Service Design can mix both the digital and the physical.
So what's a better choice? The one where you can find a job. If, in your region, there are no Service Design jobs but plenty of UX jobs, then UX will be the better starting point. If you have a deep passion for all things digital and what to specialise in that, UX is a great choice.
The reason why I still have a huge passion for Service Design today is because it works both with digital and physical aspects. And it takes into account both the users and the people who make the service work. This diversity is something I think people who are deeply curious will really love about that career path. But remember, I'm biased as fuck, I'm teaching Service Design by passion and by profession.