So we are looking for a bit smaller SUV. We currently have a Denali that my wife drives and I use as a tow vehicle for the race car/20ft enclosed trailer and goodies. We need something a bit smaller for her to drive on a daily basis pretty soon but will be keeping the Denali for tow duties and/or any heavy lifting. Having never looked at X5's before but always being a BMW guy (orginal owner of a CB/Cinn E46M3 at the moment), we would like to check them out but see several options. The 35, 35D and the 50 (M - she doesn't need a 500hp SUV). I see some advantages with the 50 that I could justify for motoring around town and in the city but I am particularly curious about the diesel reliability, fuel mileage and any out of warranty issues people are having that I cannot seem to find on here. We would like to hopefully find something that we can keep for quite some time and since I have had such great fortune with my E46 (while maintained very well), hoping I could learn from you guys here on the X5 options and get my expectations in order.

Thanks in advance!