Why would someone buy the Prowler over a Redeemer or Hoplite?

The Prowler is built for stealth deployment and emergency extraction - if you're going in quiet or coming out loud, the Prowler is an excellent choice. But just as with any other area where there are a variety of ships that can serve a certain role, each has its strengths and weaknesses and what you'll favor may depend on your play style, particular skills, and overall strategy with your fellow players, if any. It's just a cool ship, for one thing. The Prowler definitely gets style points. For another, it's a very dedicated personnel carrier that carries quite a lot of troops for its size compared to the Redeemer or Hoplite. And further, the Prowler, due to its Grav-Lev plates has a handling edge when it comes to getting through that last part of the landing approach, including fast landing and positioning, as well as hugging terrain features for cover from enemy defensive emplacements, which can be a significant advantage in a tight situation. On the flip side, the Redeemer and Hoplite are designs that more heavily incorporate considerations for direct ship-to-ship combat, being a gunship and fighter, respectively. While the Prowler does sport some pretty solid weaponry, as many fighter jocks will tell you, firepower is only one of the variables in ship-to-ship combat. What you'll want depends greatly on how you like to play - as well as what the opposition has arrayed against you.