There are all kinds of different combinations for Worlds Finest, but for the sake of this editorial, the team will be Superman and Batman. The Trinity is Batman, Superman, and Wonder Woman. And While the Justice League has more members than a small government, for the sake of this editorial let us assume the roster will be Batman, Superman, Wonder Woman, Green Lantern(Hal Jordan), Flash (Barry Allen), and Aquaman.
A quick assumption to make would be “The more, the merrier” and while this is true for many things, it may not be as easy for this situation.
A Justice League movie would likely be nothing short of jumbled and crammed unless it were handled like the Avengers, with each major member having their own movie to introduce them to audiences and provide a concrete origin. Handling it the same way as The Avengers however would take many years. Assuming each year two members had their own movies, it could take at least four years to culminate into the Justice League. And people as a whole are an impatient bunch.
Which brings us to Worlds Finest.
Batman and Superman are arguably the biggest names to ever come from comic books. The draw that comes from their names alone is tremendous. And assuming that the upcoming Man of Steel and Batman reboot are tied to the same universe, it could be a fairly quick, and relatively cheaper venture. The obvious drawback is that it would be Superman and Batman and only Superman and Batman. While this may not be a problem to many (it certainly isn’t a problem to me), some could feel like it was just a quick means of cashing in on the hype surrounding superhero crossovers started by the Marvel cinematic universe, but that Worlds Finest would only be a watered down version, since it has a much smaller roster. This is only a theory, and would be very unlikely to affect the actual movie, but people are also a fickle bunch.
Now regarding the Trinity.
Most everything that applied to Worlds Finest, also applies to the Trinity. Smaller Roster, could be completed sooner, and would be less expensive than a Justice League movie. However, one major upside to Trinity is the addition of Wonder Woman. This would be a major improvement over Worlds Finest for a number of reasons. There would be another huge comic book name attached to it. Also, it would be Wonder Womans big screen debut, and even though she would have to share the screen with Batman and Superman, this works to her favor because the general interest in Wonder Woman outside of comic books is minimal at best, so a movie with only her would likely be a financial disaster, but with Batman and Superman carrying her, perhaps everyone else will see how badass she can be. Lastly, another reason this would be an improvement over Worlds Finest would be that there is a strong female lead in a comic book movie, however this would only be an improvement if she was actually portrayed as a strong character. Portraying Wonder Woman as a damsel in distress would only hinder interest in her further.
Arguably there has not been a single strong female lead in a comic book movie ever. The best portrayal yet has been Hit-Girl from Kick-Ass. So this could be a chance to showcase that while comics are indeed a male dominated genre (much like everything else) there is a strong female presence as well.
And they can kick just as much ass as the men.