I believe the 5K also includes a better engine and a 8 speed gearbox, if it has the new Idrive..?
"2010/2011 X5 "Life Cycle Impulse" (LCI) Changes
2011 BMW X5 xDrive35d
In 2010 the X5 underwent a "Life Cycle Impulse" (LCI) update, debuted at the New York Auto show in April 2010 and introduced as 2011 models in BMW North America markets. The changes included revised styling, primarily of the front and rear bumpers, air intakes and headlights as well as new exterior and interior colors and new options combination. It also included BMW Group's latest infotainment system.
More significantly, a new range of engines, all turbocharged and with direct injection was introduced. In the North American market, available gasoline power trains are the xDrive 35i twin-scroll turbo six-cylinder and the xDrive50i twin turbo V8, both coupled to an eight-speed automatic Steptronic transmission. These petrol engines are more powerful and lighter than their predecessors, with the 35i also providing improved fuel mileage and reduced emissions. The xDrive 35d turbo diesel carries over in the NA market with the six-speed transmission unchanged from the previous model year. The xDrive40d was also introduced along with a revised xDrive30d, but neither are currently available in the North American market."