I believe 100% that a one-man SaaS needs to leverage their existing knowledge even more than a team. So for me it would be a no-brainer nodejs, dynamo, etc. - the tech I use every day and know in and out. You should have a very good reason to stray from your core if you actually want a business and not just a fun coding challenge.
This. You will want to focus on product design, customer acquisition, financing, investment etc etc. These alone are more than enough for a team, let alone one person. You don't want to be wasting your time and energy fixing server issues or obscure browser bugs at 3 am.
