Well to be honest, either MB is working closely with BMW or they decided to basically copy the general shape of the BMW X6 and make it more rounded. Regardless, it obvious that they are trying to take sales from BMW after their designers came up with a design that consumer love in the SUV market. A lot of car brands seem to be taking similar traits from each other nowadays and not incorporating the originality companies like MB stand by. It's still a great looking car because the general design is eye catching but I would still go with the BMW, in my opinion. Quality of MB has dropped quite a bit over the years.
They copied the X4 in the same way that all sedan have generally the same shape. BMW did it first, but now its just a bod style and many cars will come out that look similar. I do think that MB is moving slightly down market, but they still have Mercedes-AMG which is pushing at the top end of the brand