I don't think anyone can tell you "which will be better" to become. All fields are great and preferences will differ based on individual goals and passion.
If you're trying to pick a path I'll advise you look at both fields, what it entails, the roadmap and pick one which aligns with your passion, for now, you can always circle back if it doesn't work out well.
In general, you have to test the waters to fully know what you want to focus on one path.
The 2020 Web Developer Roadmap
Hope this helps!