996 Turbo is a totally different car, it's a proper sports car for those who want to drive it like one. The CGT is just a big luxo rocket...It's all about refinement and power, not ripping around corners and revving the crap out of the engine.
My parents, now retired and in their early 60s, recently shopped these very seriously as a replacement DD (predominately for winter use given their fleet of summer cars) for the aging STS...Usage is basically weekly groceries and a few runs per month into the city to visit my grandmother. Zero interest in anything like a 996 for those purposes, and the Bentley was the front-runner because it was big, comfy and had the best interior of anything they'd looked at.
Ultimately they bought the Quattroporte, mostly because by all reports it's a much more reliable and mechanically simpler comparable. They're about 3 months and a couple thousand kms in, and it's been problem free, and they're very happy with it......A part of my wishes they did the Bentley though.