The PL is by far the best for testing. It is often the only game for weeks when you are playing against top flight competition and both of you are sending in non-training lineups. You can test tactics, test lineups, see if blanks work for your team etc. Really it is a massive advantage already but only a knowledge one not a financial one.
Testing your own real team against a real opponent of a similar level with both running real lineups is of much, much greater value than having three games where you play a Division V squad against bots.