It will depend on which E53 you are comparing to which E70. We have an air-ride 4.8is E53 and an X35d sport package E70 on springs. I prefer the ride on the E53, but the E70 is still very capable (and enjoyable) without being harsh or uncomfortable. Both vehicles are on 20" wheels as well just to add information to the comparison.

The E70 feels more solid in build quality, kind of makes the E53 feel dated/old at times. If you have any specific questions regarding the two... LMK, I'll try to answer.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)