Wyred 4 Sound DAC owners

Fast or slow rolloff?

fast is the default setting, which is how I've used it till today. Switched to slow. Damn! 
so tell me what you like better about the slow roll off.  I have a Wyred dac 2 dsd and Femto clock upgrade and I am interested in your observations.
I too have the Femto clock which I think is a very good thing

slow = more air;  the highs just float
I have the W4S DAC.  I'd like to here more about this.
It's part of the menu options- it's there for you to try
On the W4S DSD SE, I also prefer the slow setting and feel the soundstage is more open and highs generally better.   However, with DSD the default BW setting sounds best to me after much experimentation.