PM is heavily used for gears. That is one of it's strongest applications.

Machining from solid stock is often not as strong due to grain structure issues. For a related example search the interweb on rolled threads vs cut threads.

Many parts that are sintered are also infiltrated with a lower melting metal to fill in the remaining interstices in the PM matrix.

Tungsten carbide is sintered, but is not PM as it is a ceramic. Similar process, but yet different.