In my opinion, the benefit of using MB for maintenance on a relatively new vehicle is their Mobilo service.
I contacted them around 18 to 24 months ago regarding my inability to open the fuel flap on my Mercedes-Benz GLE. The Mobilo staff advised me to take it to a Mercedes-Benz dealership. Upon contacting the dealership, I was informed of a three-week waiting period. I then called Mobilo again, and they sent their mobile service van. It turned out that no replacement part was needed, since the van already had the necessary component, which I purchased for around £40. If I had brought the vehicle to MB, I am certain that the diagnostic charge, as well as the cost of the item and its installation, would have amounted to about 400-500 pounds. Approximately 11 months later, the unit began to exhibit difficulty in opening and sometimes became stuck. Mobilio offered the option of dispatching the RAC service on the same day or the Mobilo service on the next day. The Mobilio was repaired the next day, and the flap opener was replaced once again. I am certain that it has a guarantee that lasts for 24 months.
Following the advice of others, I scheduled a B, A B service for my vehicle's automatic gearbox at the 5-year mark. It helped me save a few pounds, I suppose.