I think the depreciation would be greater on the Mazda - I just bought a 325i 2003 for $15,000.
50,000 miles - it has the sport package and the permium package = leather interior - DIY friendly - Should get another 50,000 miles out of it. Alot of car for the money.
The thing about the Mazda is you make payments - at the end of your term - it's worth -0-. With the BMW - you make payments - and it's still worth something.