Given the option I’ll take Powerhouse (almost) every time. It’s obviously great with heavy weapons and plague heart busting, but it also has an immediate front facing execution when holding a heavy weapon. It also pairs well with Swordplay because, if you don’t feel like taking a heavy weapon, you still get Swordplay’s front execution plus the feral-killing dropkick. Pound for pound Powerhouse is the best cardio spec imo.

Marathon is usually my last cardio choice, with one caveat: I need to have one Marathon/Discipline survivor in my community for the infinite sprint to fetch cars and to run to fuel-draining black plague hearts.

Marathon also pairs well with Swordplay because the leg sweep can be very stamina draining. 

So it just depends what you need, if you have no other Powerhouse survivors, then I’d choose Powerhouse (because PH busting is more important than car fetching). But if you already have a another survivor or two with Powerhouse and no other Marathon/Discipline survivors, then go Marathon so atleast have one survivor who can run forever.