My two cents and I am late to this thread.

I owned a number of the E70s including the 3.0, 3.5d, and 3.5i. One year ago I traded my 2012 3.5i for a new 2011 Acura MDX Advance which I still own.

I preferred the 3.5i to the diesel. Doing the math, the price of diesel on average was 10% more than premium unleaded, erasing quite a bit of the fuel economy advantage. I also felt the 3.5i was a better match for the X5, it was much quicker off stops and I wasn't planning on towing anything.

I traded my diesel for some of the reasons already mentioned in this thread. First the clatter was too much for me. At low speeds it was loud outside of the car, especially around my neighborhood. It just didn't feel like a premium car (I get that many people here like the sound). Also, my wife refused to fill it after visiting too many gas stations with dirty diesel pumps.

I left the 3.5i due to continued reliability issues with the X5s as a hole and due to my fatigue with run flat tires (we also sold our 328i for the same reason).

The Acura MDX Advance is a fantastic value with the adaptable suspension, blind spot detection, automatic cruise control, and emergency braking system. The MDX does lack some X5 features I liked such as the heated steering wheel, rain sensing wipers, and park distance control. I know the rub on the MDX is the center console, but I was fine with it in a day of use. (Note I also had no issue with iDrive). Our MDX has been solid, no rattles or issues except for a recall to reprogram the tranny.

Obviously there are good and bad cars from each manufacturer. Used BMWs scare the heck out of me. Even if they still have warranty, there are a bunch floating around that were traded in for problems, so be careful.

I bought 11 new BMWs over the years and have completely left the brand. My second car is now a 2012 Infiniti G37 Convertible and it also has been solid (so far).

Again, BMW is a very good car and there are great folks on this board. My X5 problems were all over the board (last one was failing brakes). As Mike Miller said in Roundel, avoid BMWs that are out of warranty (pointing to the potential emptying of your wallet).

Best of luck in your search. The X5 is a great drive, hope you find something you like.