Is asajj ventress stronger than general grievous?

Of course she is, she is much more skilled in the lightsaber and the force.

No, because she was taught by Count Dooku after he taught General Grievous. But she does have force even though General Grievous doesn't. And General Grievous taught a little bit to Asajj Ventress. Also, Asajj Ventress has two lightsabers that can turn into a saberstaff, but General Grievous has four lightsabers. Grievous also has killed 32 Jedi, and Asajj Ventress has killed none.