Even tho' you plan to pay in full, you might want to check if there are financing incentive dollars that will reduce your price. You would need to verify the minimum amount that must be financed, how many months do you need to keep the note and the APR. I believe that BMW Fin. Services will want you to finance $20,000 and keep the note for 6 payment periods to qualify for their financing incentive dollars (if the program is in place). You can always make large payments in the early months to minimize your interest. Again, my understanding is that the max monthly payment you can send them is $5,000 and I don't believe there is any early payment penalty. Also, check if you will incur any additional documentation fees by financing.
There may be other angles on this that others may wish to post, but why ignore incentive money if the bottom line math is in your favor plus, unless I'm mistaken, it should enhance your credit score.