I have not driven both F15 versions. I have driven an E70 35D and a 35I, but it has been about 2 years. To be honest, when I drove the 35D, although it was torquey, I thought it was a little, well, doggy as she wound out. The 35I (as I recall), I loved right away, and then ended up with a 50I (which I adore).

The 2nd E70 I would replace a 13 Touareg TDI that I currently also own. The Touareg TDI has an 8 speed and the entire drive train is excellent. However, there are lots of irritants with the Touareg which is leading me to get rid of it:

1. Hands free is poor (compared to E70)
2. Seats are poor (compared to E70)
3. Nav is poor (compared to E70)
4. Sports mode is kinda clunky (compared to E70)
5. Handling, although smooth and rock solid, is kinda squishy in the corners

(compared to E70 - I realize I have Adaptive Drive in our 50I, but I would aim to get AD in the next E70 too)

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2011 X5 Xdrive50i Sport Package AD
2013 Touareg TDI
2012 Ford F250 Super Duty Powerstroke
1997 BMW M3 Sedan
1995 BMW 540i 6 Speed

Retired:
2008 Acura MDX (good car - yawn)
2002 M5 (I will miss this car forever)
1999 M3 (fun car X2)
1992 325IS DINAN (fun car)
1987 325IS (fun car)
1986 325IS (fun car)