5500-2 for cost efficiency and the fact that very good aftermarket filters are available that have performance equal to that of OEM.

Do keep in mind though that the 5500-2 and all of the models you noted are mainly going to handle particulate filtration (i.e., they remove particulate matter from their air through mechanical filtration). They will do very little for adsorbing odors, or VOCs, in general, as they have only a small amount of carbon, and they will have no impact on nitrogen oxides, so their chemical filtration capability is, like most purifiers, extremely limited.

None of the Winix models noted are BIFL. AirPura, AllerAir, and Austin Air make products that would be BIFL as these are using stainless steel bodies with commercial grade motors (these are also capable of tackling VOCs as they all use large carbon filters).