We use Nego or Od when we want to compare something. Preposition OD will precedes Genitive Case where as Nego requires the same part of the speech which precedes it. If the object is a noun or a pronoun it will follow nego directly (the meaning of the sentence is the same regardless of using nego or od).
- On govori brže od nje. / He speaks faster than she does.
- On govori brže nego ona. / He speaks faster than she does.
If the object in a sentence is a verb or a phrase then we need to use Nego što.
- Ona piše brže nego što govori. / She speaks faster than she speaks.