So I'm building a site-building service

Basically a user's site like "robert.site.com" will resolve by using the subdomain "robert" as a parameter.

Now I'm stuck between using static or dynamic rendering.

a) static means I'd pre-render html files and serve it accordingly

b) dynamic means I'd have react templates and hydrate them using json

I feel like (a) creates a more brittle experience (static content not mapping 1:1) and requires storage buckets

yet (b) could have penalties on SEO and other shortcomings.

Is anyone able to weigh in? What would you go with?