Unity's built-in version control might actually be easier to use than Git... not sure, I haven't used it in years.
If you do decide to use Git or some other version control:
- It lets you upload your changes/updates as "commits". You can see all the lines of code that were changed/added/removed in each commit.
- More importantly, other contributors can submit their own commits to you as "pull requests", which you can review and have Git merge into the project without overwriting any unchanged lines.
It's mainly just useful if you want other people helping with the programming. TBH, I haven't gotten any use out of putting my mod tools (GeoTool, Arc Hammer) on GitHub so far, other than a convenient place to upload them. But those were just small side projects.