If its just fairly smooth grass the Marder out turns the Baja in most situations it handles flatter and doesn't have all the tail happy dramatics although it's still running a stock can on a G260.
It's only the bumps and ruts that the Marder just gets confused and doesn't really know what it wants to do, also the Baja can be ran hard off MX style jumps and just laps it up, I wouldn't even consider the taking the Marder anywhere near the rough stuff.
But they are 2 different machines for 2 different applications.
And the Losi runs rings around both of them, in fact the Baja has had no use since getting the Losi and the Marder is only in the garage still as I love the way it looks easily the best looking rc.