What is the best air filter/ purifier for a home?

Hepa.

After years of Upgrading, upgrading, upgrading, I found the Austin air filter. Stands about 20 inches high, but is quiet. And Yeah, it Is expensive. And the filters costs like $300(on Amazon), BUT it lasts 5 years. Being a smoker, this filter will effectively 'sterilize' my 1,000 square foot apartment in like 8 hours.
And it is better than replacing the filters on a regular basis-which can be more expensive. Spend the money upfront, cheaper in the long run.