According to the documentation you should use both together:
We recommend all production ASP.NET Core web apps call:
- The HTTPS Redirection Middleware (UseHttpsRedirection) to redirect all HTTP requests to HTTPS.
- UseHsts, HTTP Strict Transport Security Protocol (HSTS).
ASP.NET Core Enforce HTTPS
The .UseHttpsRedirection() will issue HTTP response codes redirecting from http to https. The .UseHsts() will add the HSTS response header which the client is supposed to obey.