I had an '06 RRS SC, Buck Blue/Blk and loved it. IMO it's a mistake to compare the RRS to the X5 if you actually use the off-road capabilities of the RRS. If you don't, then gas will definitely be better with the d, and the rest is personal preference.

For what it's worth, I love the on-road performance of the X, the tech is much better, the service is better, but I'd rather have an RRS for the trips to the mountains and the desert.

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Current Rides:
The Black Beast - 2010 X5M Blk/Blk / Fully Loaded (w/o RSE)
2004 BMW 530i Space Gray/Blk Sport Pkg

Favorite Past Rides:
2006 RRSport SC Buck Blue
2003 Ducati 999 yellow
2001 Ducati 996 yellow
2000 Ducati 748 yellow
1988 BMW E30 M3 Gray/Blk