I always thought Vic was every bit as sentient as the Doctor. Just different in their treatment and goals. From day one the Doctor was treated as a tool despite his brilliance. I think this is what led to his ego inflating, the desire to show everyone how invaluable and capable he is. Vic was treated as roughly an equal by everyone from day one. While the Doctor wanted to expand his horizons in the real world, doing new things such as singing, holowriting and photography, Vic just wanted the freedom to explore his holographic world beyond being turned on only to sing.