For a new project
(Sitecore PaaS) I'm wondering if it would be better to
- Run the CD with two separate web apps (both single instance) implementing the zero-downtime deployment myself in the deployment process. Using a traffic manager, etc.
- Have just one web app scaled out to 2 instances and then use deployment slots to have zero downtime deployments.
I've some experience with the first approach and I really like the fact that you are in full control of both specific web apps that are responsible for Content Delivery (being able to resolve a page on a specific web app by using a web app specific hostname). But after some googling, I get the idea that most Sitecore PaaS implementations are set up with the second option.
I couldn't find any Sitecore recommendations about this topic.