I can only speak for my experience.
The reason why I went with Houdini is not necessarily how "cool" (i.e. all the FX (pyro/fluids/particles) you can deliver) or how "procedural" it is.
It was merely because it solve a problem.
As my projects became more complex, I couldn't do it in C4D any longer.
Or if I can do it, there is just too much work around.
A straightforward example is the clones.
In C4D, you can't manipulate the individual clones freely.
I mean you can but from my experience you'll probably realize its not that manageable.
With Houdini, with the power of attributes, you can literally do anything.
When I bought xParticles. I thought okay I don't need Houdini any longer.
But not really. No offense for Insydium. xParticles is great. It can deliver of course.
But in comparison to Houdini of building a system for sustainability, xParticles just can't compare.
For example in Houdini, you can do post correction on your sim. Which is a massive plus. You don't have to just fully rely on your initial parameters.