This is the wheel i have. Two actually. One for my boys, and one for my girls. They are a metal flying saucer.
I can say from my use of them, they are pretty quite. With a few extra of the U shaped pieces that are used to attach it to the cage walls, i imagine it would be even more quite. But iv never had to do that. In all honesty, the chins them selves make more noise running around in side the cage then they do on the wheel.
Benefits of these wheels are a chin can reach full extension when running. And they can do that with out a round curve to their spine. The metal will last forever. And even if something should happen where it doesn't spin or really noisy spinning, you only have to replace the bearing which is really simple to do (and cheap). (Mine also came with an extra bearing). They are really simple to put together, but none the less, it still came fully assembled when i got min.
I personally have two sizes. One Large, and one medium. They both work. Tho i like the larger one better. It really depends on the cage and just how much room you have to use for the wheel.
This is one of the wheels i have. Momma Sophie taking a nap on it after a long day of dealing with her kits lol.
Down sides: Really only the price. Iv had mine for several years, and thats the only thing i can come up with.
Standard (medium) is US$74.95 and Large is US$83.95. Plus shipping. So its a hefty initial cost. The upside of that tho, is the wheel should last for life. And they cant chew it. Of course you can always try to find someone on line selling their wheel at a discount. (Thats how i ended up with a medium for a 2nd wheel). And should you ever find yourself not in need of it, i would imagin you would have no problem selling it.