Both of these are essentially style guides. A way of doing things.
I recommend Bootstrap because of the following points.
- The large number of websites currently using it
- The large number of contributors and bug testers on the open source project
- Being more marketable for jobs because more teams use it and you don’t have to relearn a new style guide
Ideally, you would use Bootstrap Sass as a starting point that you then adapt to your project creating your new style guide based on Bootstrap.
If you are new to Bootstrap I have a classes reference table to quickly learn its capabilities for your projects.
If you are doing this as a hobby it does not matter and comes down to preference.