How does an ASP.NET endpoint's result differ when using yield return compared to returning a populated collection?

Question

When using the return type IEnumerable<T> in a .NET 7 Web API endpoint, what is the practical difference when using yield return compared to returning a populated collection?

The following code has two example endpoints to compare the scenarios:

using Microsoft.AspNetCore.Mvc;
using Microsoft.Data.SqlClient;
using System.Data;

namespace YieldTest.Controllers;

[ApiController]
[Route("[controller]")]
public class UsersController : ControllerBase
{
    [HttpGet("yield-return")]
    public IEnumerable<UserData> YieldReturn()
    {
        using var connection = new SqlConnection(connectionString);
        using var command = new SqlCommand(query, connection);
        connection.Open();

        using var reader = command.ExecuteReader();

        while (reader.Read())
            yield return new(
                 reader.GetString("Username"),
                 reader.GetString("EMail")
             );
    }

    [HttpGet("return-collection")]
    public IEnumerable<UserData> ReturnCollection()
    {
        using var connection = new SqlConnection(connectionString);
        using var command = new SqlCommand(query, connection);
        connection.Open();

        using var reader = command.ExecuteReader();

        var users = new List<UserData>();
        while (reader.Read())
            users.Add(new(
                reader.GetString("Username"),
                reader.GetString("EMail")
            ));

        return users;
    }

    const string query = "SELECT Username, EMail FROM Users";
    const string connectionString = "Data Source=.;Initial Catalog=[db];User Id=[user];Password=[pwd];";
}

public record UserData(
    string Username,
    string Email
);