Inexpensive brakes of any design and period have inferior performance to their more pricey counterparts.
Japanese OEM single pivot sidepulls, center pulls & cantilevers of the early 80's all reduce speed well if properly set-up on true wheels.
Modern brake pads of the correct type from mfgs like Kool-Stop, well lubricated and adjusted calipers, properly installed levers and the correct length of new brake cables should be adequate for use on any 80's Miyata.

Absolute "stopping power" has never been high on my list of braking requirements, although good feel & modulation are.
Some prefer the feel of centerpull, cantilever or sidepull brakes and even choose design by application. All are available today.

-Bandera