I had the HiFi Individual (DiRAC Surround system) in my previous 2010 (F10) 5-er. It was okay, the best BMW had to offer at the time. The sound was a bit muddy, not so airy and clear but packed some punch.
I've had a loaner with HiFi for a couple of weeks now and the sound was actually very similar to the Individual HiFi in my old F10.
My new X4 have the Harman Kardon system and it is a step up in sound quality IMO. Clearer sound, more dynamics and less "muddy". I'm very happy with it.