Base64VsByteArray.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class Program
{
  public static void Main()
  {
    const string Content = "Hello World";

    var bytes = Encoding.UTF8.GetBytes(Content);
    var base64 = Convert.ToBase64String(bytes);
    var jsonBuilder = new StringBuilder();

    jsonBuilder.Append("[");
    foreach(var b in bytes) 
    {
      jsonBuilder.Append(b);
      jsonBuilder.Append(",");
    }

    jsonBuilder.Remove(jsonBuilder.Length - 1, 1);
    jsonBuilder.Append("]");

    var json = jsonBuilder.ToString();

    Console.WriteLine($"{jsonBuilder} ({jsonBuilder.Length})");
    Console.WriteLine($"{base64} ({base64.Length})");
  }
}