Azure App Service on Linux or Windows

App Service on Linux is still in preview, so stick with Windows for production environments.

For Dev/Test (or even non-critical prod environments), if you have a Node.JS or Php application Linux is the way to go because it runs Apache which offers way more performance than on Windows IIS. Additionaly, the App Service on Linux is currently 50% of the regular price.

Public Preview pricing for App Service on Linux is 50% of the regular price, and the price is calculated by halving the number of compute-hours consumed by your App Service Plan.

No SLA is offered during the public preview period.

When the Web App for Linux launched last year I was quick to perform a few basic performance tests between the two. You can find my original article here (Beware: Bing Translation from Portuguese!). While this article is definitely outdated, at that point in time, Linux was performing about two times faster than Windows for a typical WordPress Blog application. The problem I had back then was the large number of failed requests I was getting from the Linux platform that should be fixed by now.

Considering features, the Linux platform also lags behind Windows. Some features, such as virtual network integration, Azure AD, or Kudu site extensions, are not complete. There's also no Free/Shared Tier or availability beyond West US, West Europe and Southeast Asia datacenters.