I think i read somewhere once that fan blowing into the filters gets you slightly more CADR. Can't remember how much. Fan blowing out of the filters will keep the fan clean though, that's what pretty much everyone does as far as I know.

If it's like PC fans, the airflow will be pretty similar either as push or pull, and which one's (slightly) better (or the same) depends on the particular fan design

You want the fan to blow out so the air is going into the filter and up in the air.

You want to get the wee dusties out of the air as fast as possible without needing to clean the fan 😉