Some people recommend to avoid using Web Garden. Instead they recommend to try first tuning some parameters in ASP.NET app web.config file by using this.
As far as I know Web Garden consists on incrementing the number of worker processes in the Pool. It is like having multiple threads serving the incoming requests.
So what's the difference between using multiple worker processes for the Pool and tuning the ASP.NET web.config file by using parameters such as MaxWorkerThreads, MaxIOThreads, etc.?
Both consists on using more than one thread so I am not be able to see the difference between these two techniques.
I feel when working with scalability, you want to scale vertically as far as you can before scaling horizontally.
The advice you're hearing is suggesting the same thing. That you make sure to set max worker threads for one IIS instance, to give it a fighting chance. It's better to do this and increase CPU before looking to scale horizontally.