(The rating is primarily for the trilogy) Film 3 needed to do 3 things: Glide down from the emotional high of film 2's climax, build up to the climax of the Washio Sumi arc, and connect to Yuuna's arc. Content-wise, this is possible in one TV episode, but that would be quite fast, even for a YuYuYu episode. So after the introductory scene, we have a few more side stories interspersed with a buildup involving the Heroes' parents and teacher over the introduction of the Hero System that would be used in the first TV series. I quite like this build-up, as it demonstrates that while theadults in charge are as mule-headed as one might expect, not everyone was on board with using it on young girls without telling them everything.

The side stories, as in film 2, demonstrate the powerful bond among the Heroes, and despite all they've gone through, they still take the time to laugh and play together.

The climax of the arc is as epic and tragic as was implied in YuYuYu, and one thing that might've been a nice addition during the transition scenes is Karin receiving her uniform/costume, but connecting to Yuuna was probably more important.

Could someone be introduced to this universe by first watching the prequels? Possibly, but throwing elementary school girls into a combat situation like this from the outset can potentially be a turnoff, particularly since this series is much harder-hitting than the Nanoha series. Sonoko's diary entries that precede each film (and each episode in the TV version) provide foreshadowing and hints, and yet that doesn't really soften the emotional blows delivered, quite the contrary. In this respect YuYuYu is a better introduction because like most of the audience, the characters have no idea what's going on when they first face a Vertex, whereas the trio of Heroes in the Washio Sumi arc have some idea what they're in for; additionally, the introduction of Sonoko in YuYuYu reveals that perhaps there's much more to the lore than we've been led to believe. So perhaps the "Star Wars film release order" strategy is a successful one.