The E53 is a 5 speed. HP is 228 and TQ is 221. 0-62 is 8.3.
The E70 is a 6 speed. HP is 268 and TQ is 232. 0-60 is 8.1.

The difference from 0-62 is not as much as one would expect with the advantage of the 6 speed transmission and the increases in HP/TQ. There are a number of factors that could be the cause. The E70 is about 200 lbs heavier. There could be a greater loss of HP/TQ from the crank to the wheels. It could be that the ratio of first and second gears are the same as the E53 that wouldn't contribute to increase in 0-62 time. The 6th. gear may be a road gear to improve highway mileage. It could be that the height of the tires from ground to top of tire is a greater diameter.

HP and TQ numbers may be a little off depending on the source but the end result is that the E53 is two tenths faster to 62mph. Since the difference is not all that much, my choice would be based on condition, mileage, history and PPI findings (excluding price).

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas