Like UCrew said, the E53 was the original X5. It was built from 2000 to 2006, with a facelift in 2004. The E70 came out in 2007.

Throughout its life, the E53 offered a 3.0L in-line six-cylinder engine, a 4.4L V8, and a 4.6L V8. The E70 offers a slightly more powerful 3.0L in-line six-cylinder, a 4.8L V8, and a diesel (3.5L, I believe?)

The E70 is a completely new model. It's bigger, wider, heavier, but more refined (some would say "softer"). The E70 has run-flat tires standard, which do not last as long, and are expensive! The E70 also offers a third-row seat, which was never an option with the E53.

Both handle exceptionally well, especially when equipped with the Sports Package. I've owned both (though my E53 did not have the Sports package), and the E70 does handle better. The E70, obviously, has the latest and greatest in technology, but I'd have no hesitation recommending either one.

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