Honestly, for a public plaza, I’d recommend a bench without central armrests—or at most a design with armrests only at the ends. A plaza is a shared living room, so the seating should feel open and welcoming.
Center armrests are often used as a quiet way to prevent people from lying down or sleeping. That works to some extent, but it also sends a clear message: “you are not welcome to stay long.” It can make the space feel defensive and can exclude elderly people, pregnant women, children, and anyone who just needs to sit sideways or rest more fully.
That doesn’t mean you should ignore sleeping or antisocial behavior. Better management tools include good lighting, active programming, regular cleaning and maintenance, visible staff or community presence, and access to support services. Those address the real issue without turning every bench into a barrier.
So my recommendation: skip the central armrests. Keep end armrests because they help people stand up, and choose a bench profile with a comfortable backrest. If needed, use a mix of seat types—benches, movable chairs, and low walls—so the plaza stays flexible, dignified, and genuinely public.