Well the Rolls certainly doesn't suffer, it rides like butter, it wafts as they say and it actually can steer itself out of the way, a win-win for the Roller IMO.
The 5 on the other hand, not so much its been panned for its dynamics. Even using a scalled down version of the 7er platform as it does, it is still too heavy and unengaging for the enthusiasts or so they say. Oh well.
However chassis sharing is the future and its also the past, a lot of companies have been doing it for years, but the key is doing it right. VW seems to have it down in most cases.
I agree about the Panamera, but the 911 shares a lot with the Boxster, always did up until now. However both both mid and rear engined sports cars, they really have to share a lot, the expense would be extreme if they didn't, but the key is they have the same mission, sporty dynamics. The 5 and 7 don't have the same mission hence the 5 suffering because it is tied to a chassis that was built more for comfort than sport.
Oh well it is what it is.
M