when we filter a form for a specific set of records, ms access has to load the whole recordset to memory, go thru every single record and show us the subset (filtered records). This will not be a performance problem if the database & client are on the same machine.
when database & client are on 2 separate machines and linked by network, filtering a form requires the whole recordset transfered over the network from database server to client machine while using SQL statement, the query is run by database server and only the subset of records is traveling along the wire to client machine.
in short, in client/ server environment (the one you'd like to upsize) the recommendation is SQL statements and not filtering
hope this helps