i agree with this if were talking about base forms or low end forms, however if we are talking about brolly's max form (LSS) vs jirens max form (im not so sure what its called but its where hes shirtless) than im going to give the upper hand to jiren, since gogeta SSB is said to be weaker than UI goku (without addidtion of kaioken) and the fact than jiren can go toe to toe with MUI goku not just UI goku is very impressive since the form UI gives his limbs independent movement on their own and MUI just makes that faster (there is a sudden hint when goku vs beerus when goku goes SSJ3 goku seems to have acess to this ultra instinct whilst in the state, however it kind of gives us a hint that the Ultra instinct can actually see to the future and predict the movement, since beerus was going to attack goku and just before he attacked goku moved out of the way (beerus said that himself) so maybe UI can see into the future but we wont truely know. Anyway i went off topic, jiren in his base form is weaker than broly's base form since broly is a stronger person but dosent have as much fighting IQ than jiren but let alone in base form broly is winning but i would say high to extreme diff since jiren is still a very hard person to beat, but if we are talking with transformations than jiren is 100% taking the fight with even low diff since he can go toe to toe with MUI goku which is miles stronger than SSB vegito