Since you have stated that money is no object and you want the better car. Then the Porsche is hands down better then the 5.
I have driven the Panamera on the track during a Porsche driver event vs the Alpina B7, A8 and S63 and these cars just cannot compete in any level. The Panamera S with full leather will outdrive, outhustle, and has one of the best transmissions ever made SO FAR in the pdk.
After I remodel my house, and get some fianances in order, I will be getting rid of my 550i Msport for the Panamera Turbo. When I bought my 550i after a number of test drives comparing it to the Panamera S, I also thought the 550 was 95% of the car the Porsche was. The same week I got my 550i, my father picked up his P. Turbo so we decided to trade cars for a week. I will not compare acceleration because this is no contest that the Porsche wins hands down. However, all driver controls are far more intuitive and convienent in the Porsche. You have an area next to the speedometer that shows navigations, all car controls, car data, radio, ect which during a test drive is a "neat" feature but in everyday life, it is a must have. On top of that, I got 22MPG overall wth the PDK and people who have the S on various porsche websites have been getting 21+ easily overall. In my 550, I get 20 MPG overall with 100 less horsepower and an extra gear. The brakes, the suspension, and how tight the car feels is just where the porsche excels at. The only area where my Msport beats the Porsche at is value in price. My Msport was loaded up at 76,XXX with basically every option and the Panamera S I was looking at 95 and change. I should of bought the Porsche....
Just for reference in my the last 2 years I have owned a E92 M3 sedan, 997 C2s, Bmw X5 4.8, Range Rover Supercharged, MBZ E63, MBZ SL65, Caymen S ...
2011 BMW 550i~Road Eating Beater~
2010 Porsche Cayenne GTS ~ PetCspr ~
2010 Toyota Tundra 4x4 RockWarrior Edition ~ Recall Machine in Pursuit of Perfection ~