There is not a particularly great answer to this question since everyone uses their space differently, & different needs require different solutions. For our customers, we recommend that they buy cheap, .20 air filters & replace them twice a year, along with using an electronic air purifier on the indoor unit. Usually, these sell for no more than $300, but they save a myriad of problems. First, the cabinet air filters, as they r called, r much, much larger & more effective than return filters. Some even have UV lights to kill bacteria. They also do not restrict airflow as much as a return filter. Also, they r less maintenance. Some never need to be replaced, the most laborious ones need to be cleaned once a year. You do not even need return air filters with that system, however they r still a great idea to catch large particles (hair, sawdust, etc.).
The more expensive pleated filters can be great, however, they r by far the reason for most of our service calls. The reason is, they restrict far too much airflow when dirty. A regular blue filter can be completely dirty, & still not freeze ur indoor coil. The same cannot be said about pleated filters. We recommend pleated filters be changed once a month during summer to prevent freezing the coil.
In our opinion, it makes more financial sense to buy the electronic air purifier & then buy the cheap filters. After u replace 35 filters, it pays for itself, & it is far more effective. No pleated filter can kill bacteria!
Hope it helps, good luck with ur system.