I own a bunch of regs. In my current fleet, I have:
ScubaPro Mk 25 EVO/G260 (x2, for doubles)
Dive Rite XT1/XT4 (x2, for sidemount)
Halcyon H75P/Halo (Halo x 2, for single tank - same as G250V?)
I love my G260s. I've had them the longest of the above list. Never had them serviced, nor had a lick of trouble with them. I've never using anything that I thought breathed better.
I've had the Halcyon single tank set for about a year and a half or so. I've had nothing but trouble with the Halos. Both of them do the same thing and now another person at my shop that has them is having the same issue. They breathe fine at first. But, over time - say, after 10 dives or so - they start breathing "funny". If I inhale very, very slowly, I can get air. If I increase my inhale effort, I can feel a distinct "pop" and then they really flow a lot (like they are supposed to).
I took them directly to Halcyon HQ in High Springs and asked them to look at them. They worked on them and gave them back. Same thing. Worked okay for a short while, then back to resistance and a distinct pop. We rebuilt the 2nds at my shop. Same thing. Worked okay for a bit, then same old thing.
We talked to H and they said they had some with a bad batch of levers. They sent us new levers. We put the levers in and new service kits again. Same thing.
When they are "fresh", they breathe well. But, once they start acting up, they breathe like crap. It happens to both the Halos I have and, like I said, another instructor at the shop got a set recently and his are doing the same thing.
I got the Dive Rite XT1/XT4 set a few months ago. I've only used them in sidemount and also in sidemount with a Choptima CCR, so I haven't used them a lot. I do also have a set of XT1/XT2, which I've had the longest of all my current regs. The XT1/2 set has been great. No complaints at all.
The XT1/4 set has been great, so far. I have not breathed on them back to back with my G260s, but I have not noticed anything about the XT4 that seems "lesser" in any way. They breathe very well.
You didn't mention these, so I'll keep this part quick. I also have Atomic M1 regs (for doubles) and had Atomic Z2 regs for single tank (before the Halcyon). Both Atomics breathed the same, as far as I can tell. And, I think they breathe just as well as my G260s.
Of them all, if I were picking just one reg set to have, it would be the Atomic M1s. For single tank, and with a little bit of consideration to budget, the Atomic Z2.
As for regs being "quiet" or not, I can only say that I don't really notice any of my current regs being noisy. But, I did have a pair of SP Mk25 EVO/S620Ti regs (a pair, for doubles). Those S620Ti regs were LOUD in the water. The G260 (and the others) is SO much quieter in the water than the S620Ti was. I never realized there was really any difference in noise in the water from 2nd stages until I had those S620Ti regs.