Why did Apocalypse choose Psylocke and Angel?

Question

In X-Men: Apocalypse, Apocalypse chooses to surround himself with four mutants whom he has personally empowered to become stronger. In the opening clip, we see the original four had:

1. Death powers (we see him turn someone into a skeleton)
2. Fire manipulation
3. Extreme strength
4. Telekinesis and force-field projection

While Magneto and Storm are on the same sort of level, it seems that compared to those four Psylocke and Angel have very limited and self-contained powers, so why would they be of interest to him?

Answer 1

It's worth noting that Apocalypse doesn't just select mutants based on their skills but also their suitability as potential henchmen. Psylocke isn't just an Omega Level mutant but also a psychopath who enjoys killing and has moved from one influential leader to the next, making her the perfect follower.

The way that I see Psylocke is as a very powerful weapon that has been used and abused by different people so that they could use her powers, and she’s somebody who’s just looking for righteous purpose. Right now, that’s why she’s one of the bad guys.. She’s definitely someone who’s very strong, who’s been through a lot. She has really powerful abilities and is just looking for a purpose.

...

The thing about Psylocke is that, I can see the way that she’s dressed but it has nothing to do with how strong she is and how powerful she is. That is something that I love about Psylocke. When most superheroes don’t enjoy killing or don’t want to kill but they will kill if they have to, Psylocke can create anything with her mind. She can kill from afar, like Magneto or Storm, but she chooses to create a sword, which is a very intimate way to kill someone. She experiences it.

_{^{‘X-Men: Apocalypse’ Star Olivia Munn on Why She Ditched ‘Deadpool’}}

Angel, by comparison, is Psylocke's recommendation to Apocalypse. He seems to relish the idea of having an angelic follower, especially one with superior fighting capabilities and a deep, unbridled hatred for the humans who enslaved him. He's not the strongest mutant out there, but enhancing his powers and giving him a renewed sense of purpose seems to have made him into an uber-loyal bag-carrier for Apocalypse.

Answer 2

They were of interest for various reasons, but ultimately Apocalypse isn't very picky (at least initially) about the horsemen that he picks because he expects them to die and be replaced by more powerful mutants over time.

Storm was very easy to manipulate into following him, and she provided some information about how to find other mutants to recruit, which benefitted him (she leads him to Caliban).

The next mutant he recruited was Psylocke, who because of working with Caliban was able to lead him to even more powerful mutants, which again was useful to him as a next step.

Psylocke: I know the kind of mutants you are looking for. And I know where to find them.

Next up is Angel, who has shown that he is capable of defeating other mutants in 1-on-1 combat in the cage match scene - it's why Psylocke leads Apocalypse to him in the first place. He also has the ability of flight (this ends up being useful in the final battle, even though he is eventually defeated).

Finally, Magneto is a particularly powerful mutant who is instrumental for Apocalypse's plan.

Apocalypse: Reach, as deep as you can. You'll find you have the power to move the very Earth itself. Everything they've built will fall! And from the ashes of their world, we'll build a better one!

So they do all have some use to him in the moment, but Apocalypse doesn't seem particularly picky about who they are - for instance, Storm is literally the first mutant that he encounters. He is also clearly not attached to them, as shown by his reaction to Angel's death:

Apocalypse: Useless.

Overall, Apocalypse's goal is dead simple: the strong will survive and the weak will die.

Apocalypse: Wipe clean this world. And we will lead those that survived.

And later on:

Apocalypse: To tell the strongest among you... Those with the greatest power. This earth will be yours.

In light of that philosophy, his recruitment method seems clear. He isn't picky about who his horsemen are initially because he knows the weaker ones will die off and be replaced by more and more powerful ones over time.