A) XD35i or XD50i?
Or 50i or 35d. Depend from your (or your wife) spirits. 
B) Any regrets? Either about getting an X5 and not an X6 or vice versa?
X5 is the same technical but more family and less aggressive than X6.
C) How has relaibilty been with the X6 ?
The shit like all BMW
If serious the same like X5. Lexus more reliabilty, but 
. Guaranty help you.
D) XD35i, does it have the Same HPFP issues as the 335? This is primarily why I'm leaning towards the XD50i and stayed away from the 335.
I use x6, my wife use x5. Sometime we change.