I’d say you need to evaluate what you really want/need from a car, as the Focus and BRZ are very different. Both are fun to drive, and both are fairly easy to work on and mod. If you need a vehicle with space and practicality, the Focus is the better one to get. If you want a true drivers car, the 86’s are great sports cars that are a blank canvas to do whatever you want with (autocross, track days, drifting, stancing, etc…).
You really should test drive an 86 to see if you will be wanting for more power, cause fast cars they are not in stock form. But they have enough power stock to have lots of fun at safe and legal speeds.
The Focus is very easy to mod to get big power gains from since it’s already turbocharged, so if you only want cheap speed, go that route. Also they are great to throw around an autox as the braking assist makes it do amazing things.
Good video review of a fr-s