Remember the BMW system was initially designed in the early 90s and has been improved since then - but still runs on principally the same architechture. The first BMW nav system appeared in 1994, with what we now call the Mk1. A 2002 X5 will likely have a Mk3, maxbe a Mk4.

The Mk4 system is still being fitted to some 2008 model BMWs (Z4, X3), and software is still being developed, albeit it appears to be bugfixes only. The latest software release was March 2008.

If the Mercedes system is a new one designed in 2000, then you could easily have a decade of difference between the system designs.

And a decade is very long in computer terms....