control block and DSP Builder

My Experience:

As far as I know, configuration parameters are available in DSP Builder. The problem however is synthesis control. When you code HDL and your timing is not met, you can do many efforts in order to speed up your circuits. You may pipeline your code, register some internal wire, change your adder, etc.

In DSP Builder all of these options are not simply available. You are still able to for example pipeline your IP Core (If it has this option as in divider for instance), but your options are a few.

I have experienced this issue in another vendor tool and finally I was told by the tool that I have to export my project and perform some tasks outside DSP Builder which meant it has less power compared to the main flow.

Afterwards, I do not use DSP builder, since all IP cores are also available in MegaWizard/IP Catalog. HDL coding may be prohibited, but this is not a difficult task for an experienced hardware designer.

You are free when you design based on HDL.