1. After the partition between the children of your grandfather your father is the absolute owner of the property which he received through partition. As a corollary thereto, he is at liberty to gift or will it to anyone he desires. He has the freedom to discriminate among his children at the time of transfer of his property.
2. The property is not ancestral.
3. The will would become operative after his demise, whereas the gift deed will immediately result in the transfer of ownership.