saturday is the "big" klubnacht, running from saturday midnight to approx. monday noon. the berghain floor is the hard one (techno), the panorama bar focus mostly on house and techno (but also acts like maceo plex play there - so it depends how you define "hard")
fridays sound depends on the event with all kind of possible music (can be residents, label nights...)- nevertheless it's always high quality. seveal weeks ago they opened a new floor for more dark and experimental stuff (afaik 1x friday per month). and don't worry - there are ways to panaroma bar without going through the berghain floor.
I often heard that it's easier to get in on friday, but I cannot judge this. moreover i heard that it's easier to come "back" on saturday you already were there on friday and have a stamp...