I tried both. 3.0 was OK, but just OK. You see, if I am going to splurge (no better word) that much money on a car, I want to get it "all", including plenty of power. If you have $65K to spend on a loaded X5 3.0, I am pretty sure you have $72K for 4.8 !

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His : 2013 X5 3.5d Deep Sea Blue/Black/Aluminum with ALL packages, 20" 214"s, running boards, Adaptive Drive, Spare Tire, BMW Apps
On Order : 2016 X3 3.5 MSport Silver/Mocha with DHP, CW, Prem, Tech, DA, Lighting

Hers : 2015 328xi MSport Silver/Red

Prior:
2008 X5 4.8
2011 X5 3.5d
2010 335 xDrive
2013 335 xDrive