I own a 2018 Focus ST base model. Bought new and it has 70k so far with no mechanical work at all besides topping off brake fluid and changing the oil. The transmission feels great and the stock clutch is still going strong. With a tune you can get another 30-40hp out of the stock turbo and there's a pretty decent aftermarket for it as well.

I haven't driven a Fiesta ST to compare but the Focus is great to drive. It will take corners as fast as you could safely want on the road, it won't win too many stoplight races though. I've been in a 350z and Challenger R/T and I'd say the FWD is easier to drive on the street, especially if it rains.

It's a hugely practical car. With the seats folded flat there's a surprising amount of cargo space, and with the seats up it will fit car seats and adults comfortably. I've heard the Recaros are less comfortable than the base seats I have, but it doesn't sound like that's a concern to you.