Sometimes you may consider using controllers for all blocks, instead of just having the view engine select the correct view. As far as I know the only real difference is performance. But how much will performance be affected if you choose to use controllers for all blocks? 

TL;DR: around 10% better performance without controller, according to my tests.

A while ago I was working on a CMS-implementation which needed a somewhat complex multi-site architecture. I had to choose between using controllers for all blocks, or being forced to use a bit limiting naming convention for blocks. When I made the decision I didn’t know how much using controllers would affect performance. Next time I’m in a similar situation I will know, because I just did  some load testing using the lovely free tool Netling 

Note that the performance testing I have done are quite un-scientific, but it should at least give a hint. I created a block that basically did nothing, and a controller that just returned the view for that block. Then I just started the site from Visual Studio (IIS Express + LocalDb), and let Netling hit it a couple of times.

The result

This is how my laptop performed

Without controller

A single block in a content area: Around 215 requests per second
Five blocks in a content area: Around 205 requests per second
Ten blocks in a content area: Around 190 requests per second

With controller

A single block in a content area: Around 200 requests per second
Five blocks in a content area: Around 175 requests per second
Ten blocks in a content area: Around 160 requests per second

7-15 % is not that much, but it’s not nothing either. I will continue to avoid using controllers for blocks, but I’m glad to know that it’s not that big of a deal.

At time of writing I was using Episerver CMS 10.10.4.0