Being that you're in Germany, get the M4. I would get it with the expectation of letting it go after the lease. But the experience over two years would determine my final course of action and whether buying it or leasing a new one is in the running.
If you weren't buying a BMW in Germany, I would agree with the don't bother consensus. But I don't think I would pass up that deal with the Autobahn nearby.
GL whatever you choose
