Unlike the American, Indian, Japanese, British, or French metros I’ve been on, transit in the German-speaking part of the world has no fare gates. Instead, they use proof-of-payment i.e. random checking by inspectors and fines if you fail to show a valid ticket. I’ve previously encountered these on commuter rail (Mumbai Local, Caltrain), but Germany and Switzerland use it everywhere, including on buses, trams, and urban rail. Having extensively used transit in Berlin and Zürich on a recent trip, I can confidently say this is the superior system. There are many reasons for this:

• Easier to navigate: Trying to make a connection at a giant interchange station can be daunting in a new city. It’s even worse when accidentally going the wrong way means exiting the station and paying a new fare (this happened to me in Boston). Train stations in Berlin, though, felt very open — even large ones like the Hauptbahnhof. And if you end up on the wrong platform, or outside the station, you can just walk back in
• Simpler station design: the average non-interchange underground station in Berlin is simply a staircase or elevator leading to the platform. There is no need for a mezzanine level with ticket machines and additional circulation area before the gates, because the ticket machines are just put directly on the platform. Alon levy has spoken about how this lowers construction costs, but it also leads to less walking for travelers, which I appreciated
• More exits: I observed the average station in Berlin had a lot more exits than, say, BART does. This probably follows from the simpler station design, and lower cost of building an additional entrance
• Better Accessibility: Wheelchair access is important, and designing for it also helps people traveling with strollers or luggage. Fare control is often one of the choke points where accessibility gets tricky. In Paris last week, as we were taking the métro to the airport, we really struggled with turnstiles. My dad tagged his card and pushed his suitcase through first, but then the turnstile locked and he couldn’t get through himself (he ended up jumping the turnstile to get in). We could have looked for a wider wheelchair entrance or pushed the bag under the gate, but this problem would never have happened in Berlin, since turnstiles don’t exist there
• Easier transfers: London generally doesn’t let you re-enter the fare zone once you exit. Certain stations that are close by but not connected inside the fare zone allow free out-of-station transfers within specific time limits, but it’s a complicated system that even locals find confusing. In Berlin, in contrast, an out-of-station transfer is functionally the same as an in-station one, since the concept of a fare zone does not exist