Q. What is the difference between Vento Comfortline and Skoda Rapid Ambition

It is all some specification difference, it would be best if you compare cars online -- just type compare cars in google you will get couple of links that will give you a clear picture

Anti roll bar in rapid is good to take curves faster. otherwise same.

Both are sister concern as engine is same only look wise now Rapid have changed their look or else everything is same.