I don't get where people are declaring Murray better than Brown by comparing numbers from only this year. You need to look at their total body of work not just the 30 or so games from this year. If Jaylen is hitting his threes at an average of his first two years, it's pretty easy to see Brown is the better player, especially given his reduced role limiting his ability to put up big numbers and seeing what he did during the playoffs which are played at a different level than regular season games.
Murray scores more for his career. Murray has more winshares in his career. Murray averages more assists. Their rebound numbers are comparable (which is pretty sad since Brown is much larger). Murray has a better VORP and BPM.
You don't have to look at this year to reach the conclusion that Murray has performed better than Brown in their entire careers. Brown is a better defender, but right now he has been a worse overall offensive player.
Well, Murray is definitely a more prolific offensive player, has played more minutes and gets far more touches of the ball than Brown in their respective roles. The PER, VORP and BPM are all going to be affected by the higher usage so it's not surprising that Murray shows better numbers there.
Brown's career DRB% of 13.8% is a fairly clear step up from Murray's 10.3%, though. 'Not sure why you are saying their rebounding is comparable.
Where Brown's value clearly shows is on the defensive end. Using last year's much larger sample, it is illustrative to look at their shot contention numbers.
Murray played 31.7 mpg, defended 5.3 shots per game, allowing his opponents to shoot +6.0% above their average FG%.
Brown played 30.7 mpg, defended 9.4 shots per game, holding his opponents to shoot -5.7% below their average FG%.
So, Brown (a) contested far more shots per game and (b) was massively, massively better at suppressing their effectiveness. This shows a glimpse of the huge difference in their defensive value. The sample sizes were smaller in their rookie year, but Brown held a distinct edge that year as well, -4.3% compared to -0.9% on more shots defended (5.3 vs 3.3).
This year, Brown actually started off the year pretty rocky on defense, with uncharacteristic positive DFG% differentials in the first few weeks. But that seems to have turned around and he's already driven that number negative, to -1.1%. I expect by the end of the year he'll finish again with a much better differential on more shots defended. Murray has done better this year than last year, with a differential of -0.2%. That (league average) may be his ceiling on defense, though. Brown's shot-contention numbers put him among the upper tier defenders in the NBA.
I don't want to belittle Brown's struggles on the offensive end. As I said, he's really struggled with that 3PT shot and he needs to snap out of it. But if he can get on a little tear and bring that back up to even 'average', his massive edge in defensive value makes him an extremely valuable player.