Naturally, because they are siblings, comparisons are expected. Also it doesn't help that Umar hasn't done anything in the public eye before BB15, so people are bound to compare him with Asim's game as a reference point. However, I think there is yet another huge reason why comparisons will be made: fan base.
As soon as Umar came forth as a contestant, Asim Squad celebrated it and began claiming their support for him. Asim, who is known to be a distant guy from social media also made himself active on Twitter (which he almost never was consistently) and seems to have decided to play the fanbase pillar role Umar played for him during BB13.
Thus, the biggest question now is: Will the Asim fans stay connected with Umar?
Personally, I loved Asim in season 13 and I think Umar is doing well so far, but I doubt the majority of Asim Squad will keep supporting him. The reason is simple. They are entirely different. Asim was raw, hungry, and clueless when he started. I remember the first torture task where Koena (I think) applied some hair removal cream on his skin and he just got up and left. He had no idea how to play the game. He used to blindly follow Abu, Sidharth, and to a lesser degree Shefali, Arti. But the real beauty of his game was to watch him grow. He slowly separated himself from the group, became independent, built his own group, and emerged to be one of the best players ever by the end of his run. He was a true underdog. Meanwhile, Umar is the opposite of an underdog. He has watched the game closely for years and is taking very calculative moves. He got a built in fanbase without earning it. And he doesn't have that rawness Asim had because he is already starting with a solid understanding of the game. Even the others are taking him damn seriously, while no one took Asim seriously in the beginning.
So, considering the fact that Asim's fanbase are drawn towards underdog stories, will they continue their support for Umar? Or will Umar slowly have to build his own unique fanbase to survive in the game longterm?