Choose GitHub Pages when a public repo should publish itself and you will not use it as a commercial business site. Choose Netlify when you need preview deploys, forms, or redirects and you can move to a paid plan once the free caps bind.
GitHub Pages
Static hosting from a public GitHub repository
Free for public repos
Strengths
No extra host to manage for a public repo
Deploys from Actions
Limits
A private repo needs a paid GitHub plan
GitHub does not allow Pages as a commercial business site