WRITTEN BY RIYA DUBEY
Vegeta is the second lead of the entire 'Dragon Ball' series. He is also very aggressive and hence, suits the ultra Ego form perfectly. The god of destruction of universe 7 Beerus, taught this particular form to Vegeta.
Jiren is an alien from universe 11. Jiren is considered one of the strongest mortals in the entire multiverse, he is even stronger than the god of destruction of his universe.
It is unlikely that the two will ever fight, but if hypothetically, they do fight, Vegeta has the upper hand. If they were to fight during the tournament of power, Jiren would win.
However, if Ultra Ego Vegeta is the one fighting him, then he would most likely win the fight. Goku in his MUI form was able to easily deal with Jiren. Ultra ego Vegeta was able to almost defeat Granolah, which even UI Goku had trouble with.
In addition to that, Vegeta is learning the powers of a god of destruction, the strongest of which is Hakai. Once he successfully learns the ability, he will easily be able to defeat Jiren.
In addition to that, Vegeta gets stronger the more he gets hit. This implies that he will only get stronger the more Jiren hits him. This will lead to him winning the fight.
Jiren is extremely powerful as well and he has more endurance. During the tournament of powers his true abilities were shown and defeating him won't be easy for Vegeta.
However, the bottom line is, Ultra Ego Vegeta most likely wins the fight against Jiren.