We have 3 Holmes Air Purifiers/Ionizers and we have run them every night in the girls and our room since shortly after Erica was born, so we are talking 6+ years and the things still run great. So as far an longevity, I can vouch for Holmes.
I found the 3rd one at a thrift store, not working. I tore it completely apart, cleaned it all out, oiled the motor and now we have 3. So, I might add too, easy to fix.
As for noise, my girls are highly attached to the noise of these things. They went to a sleepover and had to come home to get the purifier because it was too quiet.
I like them because they block out the morning noise and help me sleep longer.