I had no issue with a Delphi sensor in my 204 (couldn't get an MB one quick enough), but you're right, the genuine article is cheap enough to use that in preference to aftermarket.
Toyota RAV4 3dr , SLK55amg, ML320 (2 ) A210 , E320 ( all gone )
Buying a cheap speed sensor on eBay is not the same as buying from MB , never suggested MB made them , just that the quality is better than a random low price eBay item.