There are three primary GPS satellite systems in the world right now. USA, EU and Russia. GPS systems use a small number of satellites in a high earth orbit.
Both the US and EU systems have an equatorial orbit, which covers most of the world's populated land mass and navigation routes. Russia's GPS satellite are in a polar orbit to extend coverage to the north polar region (and south polar), which is a blind spot for the US and EU. IIRC, Japan has a GPS system focused on the North Pacific.
Most US spec GPS chips will use both US and EU satellites. Most of the middle to high end air and marine GPS will add in the Russia satellites.
The primary reason China would invest in their own system is military. A secondary reason is to equip the really cheap cell phones they are flooding the third world with to match up with the Hawai (sp) cell systems they are spreading into countries.
My opinions….