I have a confusion regarding the use of the idion mentioned in the title. Can any one help me chose from the following options please. Appreciate your help in advance.
Option 1: Useful mainly for X,not for Y
Option 2: Useful mainly for X, and not for Y
Option 3: Useful mainly for X,not Y (Plz note the exclusion of "For" before Y)
This is a question of style, not grammar. All three are perfectly acceptable; the choice depends on the rhythm of the whole sentence. If you quote the entire passage, three sentences or so, it'll be possible to suggest which alternative is the best one.