[TurtleBoy]

There is a huge difference between the X3 and X5 as far as comfort, luxury, options, etc. so there is no way to spec the two the same. In my opinion your first decision should be whether you want to have an X3 or an X5.

Vehicles take the biggest depreciation hit in the first couple of years so it would be least expensive to buy a 2 or 3 year old X5 versus a new one if you are going to sell in three years. I have attached a depreciation curve and table for the X5 according to

That said, I would suggest not looking at the from a money point of view but rather which would you want or feel more comfortable with. If it was me I wouldn't even consider getting a used one but I have always purchased or leased new. I like to have a vehicle from the beginning of its life so I know the history, maintenance, usage. etc. Many, perhaps most, do not espouse that notion and are very comfortable buying used since it usually is less expensive.

Another thing to keep in mind is your discount program, that makes a new vehicle much less expensive than usual and you won't have that savings with a use one so that cuts down on the depreciation/cost difference.