Dad’s short answer: In order: real floor suction, dual-edge cleaning, a hot-water self-clean, a dry cycle you can feel, and an effective hair comb. Everything else — app control, display size, mode count — is a tiebreaker.

The five that matter, in order

Real floor suction comes first because it's the mechanism. Without it the machine is a powered string mop, and I've tested one that was exactly that.

Dual-edge cleaning is second, because it changes how the machine feels every single time you use it. Single-side means constantly turning the machine to face a wall.

A hot-water self-clean is third. It's what gets the roller genuinely clean rather than wet, and it's why some machines age well and others start smelling.

A dry cycle with airflow you can actually feel is fourth, and it's tied to the third. Test it with your hand rather than trusting the spec.

An effective comb in the roller housing is fifth, and it moves up the list to second or third if anyone in your house has long hair or you've got a shedding dog.

What you can ignore

Mode count. Three well-tuned modes beat eight that nobody can tell apart. Auto with a dirt sensor is what you'll actually use.

Display size. A big screen is nice; it doesn't clean anything.

App control, as covered elsewhere — pair it once for firmware and then ignore it.

Steam claims on a floor washer. Almost always hot water, not steam.

And extremely high suction numbers on their own. Suction matters here, but past the point where the dirty tank is filling properly, more pascals is the same marketing race as everywhere else.

Dad’s Take: Suction, both edges, hot wash, real drying, a good comb. Get those five right and the rest is decoration.