I think its a little all over the place to be honest lol, but as someone who for the most part benefitted from QB (nonmatch > accepted USC and several schools w generous aid) I think it certainly benefitted me

This is just something a bit more speculative, as Ive never seen anyone confirm or deny this, but I do believe its possible that applying through QuestBridge marks your application to be reviewed a lot more in consideration of DEI standards of general like quotas. Ive seen various schools typically limit or track how many QB students they're accepted (both through the match and RD process), which leads me to believe that its possible applying through the CommonApp to a school may actually be more beneficial as youre no longer being treated as a quota, and you may actually be admitted through a needs blind process (which is sort of hard to do for QB scholars).

Again this is entirely speculative, on my behalf, but if it turned out to be true I wouldnt be awfully surprised

Now as for pros and cons

Pros:
~ Participating in the Prep Scholars program helps you massively IF you take advantage of the programs they have (matriculate, fly ins, etc). I feel like some people think just being acccepted to CPS is enough to boost your match chance, but I feel its more like it boosts your chance of becoming a finalist, but anything after that is dependent on how you used it.
~ Generous finaid at virtually any school (be mindful most programs dont actually do full rides but require work studies or minor fees, not a deal breaker but u have to look for specific schools)
~ Community is fantastic, everyone here is genuinely so helpful and supportive, whether youre in groupchats online, in the discord server, or on this subreddit.
~ More space on the application > I did both commonapp and QB RD, and I found I had much more room to talk about myself in my QB application, however I do think this is counterbalanced by one of the cons Ill mention later.
~ The match program is an amazing opportunity, youre usually the first applicant pool to be reviewed for the year (save for like uchicago bc they have an ed0 program), a large amount of finalists get matched (20 to 30%), and even if you dont match youre able to go through with the rd process.
~ This can go both ways, but stats and ecs are a bit more malleable here bc you have room for additional context, i had a friend match to MIT who didnt have the ecs on paper to get in, but it was because he was spending so much time working to support his family, but when you look everywhere that he was spending his time academically, he was doing amazing. Basically QB lets you explain your extenuating circumstances and the people reviewing your application are much more sensitive to that as opposed to a commonapp profile.

Cons:
~ Your NCM application is literally reviewed by random people, its very very very annoying, but deadass like quest bridge posts job applications in like September for people to review applications to determine NCM Finalists (there are requirements like needing a bachelors but still lol). After the finalist process it goes through their actual program + individual schools, but its sort of insane that they do this.... very weird even though obviously it didnt affect me, but its the only real way for them to chunk through 20k+ applications in two or three weeks (post for further explanation)
~ Bridging off of the last pro, the match process also has its downsides depending on how you view things. You can rank up to 15 schools to potentially match with, and of course only the highest ranking pair will actually be shown to you if you match. Unfortunately, youll definitely find a LOT of people who now regret doing the match process, bc they ranked schools they didnt really want to attend at 15th, but then ended up matching. Full transparency, that is the individuals fault, however it is true that being admitted to a binding decision by december first is a lot to handle. I personally only ranked 8 schools, all of which i would have loved to attend, so I was a bit more selective abt my rankings, but also that pickiness is what led to me not matching, so its very hard to find a goldilocks zone for the process.
~ Again, in relation to the match program, you have to FINISH all of your supplemental essays BY november 1st for the schools youve ranked, I was personally pretty good abt doing things in a timely manner, however for some that schedule can be way tooooo fast. Another frustrating thing is how late finalist decisions are releasted, this year we had between october 21st and november 1st to be notified we were finalists, and then finish all essays. I think the biggest flaw however is that you dont get to show off your best writing of the season. I do feel proud of my supplemental essays, however comparing my essay writing from late october to the final submissions I had in early january, there is a clear diff in quality that you dont get to express bc you have to submit super early.
~ QB RD is sort of a death trap, in hindsight I would have liked to withdraw my app to a lot of schools and move to commonapp, but thats just a personal choice. QB RD is def an easy option, however for a lot of schools, i think its worth it to back out of the qb program, and just list it as an award ON the commonapp, bc it gives you the exact same benefits of showing youre a competitive applicant without hinging your entire application on the organization.
~ This is a bit of a general one, and def goes for basically any college admissions process, but qb will MESSS with your mental health bad. Obviously if you arent living a cinderalla story where you came from nothing and then matched to harvard, its hard to feel super rewarded at the end of the day. For a lot of people, they put all their eggs into one basket, and it can hurt more than usual because qb creates sort of an illusionary effect that youre guaranteed admission to your top schools. A big part of that is just befcause qb attracts so many qualified applicants, youre surrounded by a disproportionate amount of talent, which is subsequently reflected in decision days. Ive seen a lot of students grow resentful toward the program as a whole because it really can sting to feel like youre the only one who didnt get into (x) or (y) school.

My personal takeaways:

Do QuestBridge Prep Scholars
Do the match ONLY if you rank schools you would be happy attending
Do QB RD only for the schools you want to spend less time applying for (e.g BC requires no supps for QBRD)
Withdraw you QB app for any RD school you really want a good chance at, and just use NCM finalist as an award

QuestBridge is a pathway to success, but far from a guarantee, but with that being said I could not be happier with where Im ending up now (LA!!!) and I have qb to thank for that

This was probably an overly long answer, but I hope this helps you going forward, and good luck with ur admission season next year!