
Coway
Airmega AP-1512HH Mighty
Durable, effective for allergens/odors, but loud on high.

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I have returned two of the costco ones now. Within a months the bearings became loose ans they were way too loud for my overstimulated self. The older winix models lasted years before bearings gave out. I won’t be buying from the brand again.
I just got the winix...and if you make a schedule for it to turn on and off at certain times , plasma doesn't turn on automatically ! I can't compare the 2, but I'm satisfied with the winix.
Actually...it doesn't make a sound when I turn it on and off from the app. Also no sound with the scheduling
It's not in my bedroom, but it's always on low here. And it's very quiet.
I just started using two Winix 610s and a 909 this week. Connected to the app over WiFi with no problems and happy with the (low) noise level. We have four cats and are fostering two more at any given time. Hoping this helps with irritants & odors.
I have two of these (c610) about 2 years, just upgraded to larger units and moved them to the smaller rooms. They did help with allergies, they don't seem to touch smells. With that being said, the larger units do more at least for us so the c909 may be better depending on room size and your goals.
I have just now had my second c610 fail just under the two year mark.get it from Costco for the longer warranty while it's on sale if you can. Customer support with winix was relatively painless to deal with. I know several others with the unit and one other with a failed unit. It's pretty quiet on all but turbo. Turbo sounds like a jet engine.
Interesting, I have not had much of a smell from that one but many brands do bother me, I haven't bought a filter recently so it could have changed though.
I have a winix 610 from Costco, not quite the same as what you are asking, but If I unplug and move it to a different room, when I plug it back in it comes on automatically at the same setting it was last at. It does connect to the app/wifi
I just don't for sure know if it's the same for like a power outage or extended period of time being off. I have only unplugged it and took to a different room or some such and it always comes back on right away with the same settings it was left on.
I'm very sensitive to smells, and the smell of most new HEPA filters make me feel sick and lightheaded when I run the machine. I've not had this issue with my Bissell air purifiers, but they have been discontinued and you can't get the filters any more. I've tried a Coway and Winix so far and the HEPA filter in both has such a strong smell I can't tolerate it. I tried airing out the Coway filter for a few days and while it improved the smell was still too strong. I ran the purifiers without the filters and didn't have an issue, so I know it's the HEPA filters themselves, likely a glue or something that is used to make them that I'm sensitive to. I have a Winix from costco I'm currently running outside to see if that can help, but so far it still smells too strong. Does anyone know any purifier brands that use filters that don't have a strong odor, or use different materials? I've googled this question and looked it up on reddit, and while it seems like I'm not the only one with this problem I haven't seen any reliable brand suggestions. I mostly need something for pollen allergies, dust and cat allergies (I have asthma) and would be open to non-HEPA filters if I can get most of the benefits without feeling sick. I'm in the US and it can be for any room size. No budget. Thanks!
The C610. It's the cylindrical one.
I'm on mobile browser so it's hard to link so I'll just tell ya! We have the C535 for all the common areas, and the C610 in all our bedrooms. Then for the bathrooms and pantry we use the LEVOIT Mini Cores (I like these for small areas, but I have to change the filters more frequently.)

Coway
Airmega AP-1512HH Mighty
Durable, effective for allergens/odors, but loud on high.

Levoit
Vital 200S-P
Smart, effective dust/odor; some find replacement filters pricey.

Winix
5500-2
Budget king, durable; poor VOC removal, Plasmawave disliked.

Coway
Airmega Mighty
Durable, great for allergies/dust, responsive auto-fan.

Winix
5510 & 5520
Good value, durable, effective for pets; carbon filter issues.

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Coway - Airmega AP-1512HH Mighty