You are, of course, correct. However, the important thing about the S6 is that it is an AGM so it wont spill if it gets turned over for any reason and it wont vent fumes. This is really important for the 360/F430 as the battery is inside the cabin (underneath the passenger footrest).
The 4200 battery is in the boot so there's less risk to your health if the battery did spill/vent.