That's one area the E70 shines. Much more refined cabin as far as noise and materials. I love the E53, but it feels dated when I get into the wife's E70. Even the E61 makes it feel "old."

As for reliability. They've both been comparable as far as costs. Not bad. $500-2000 per year doing your own work. Had to repair some of the emissions stuff on the E70 diesel but it wasn't too bad (NOX sensors and active urea tank). Did the glow plugs and module as well. It has 165000 on it now and throws no check engine lights... Buuuuuuut it does need a trans because the E clutch bearing/bushing went out in the trans. So, there's that. E53's can suffer from this as well so I don't blame the E70 chassis.

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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)