Bro as far as my knowledge is concern, i agree with gull that it depends on the type of Hardware. Different type of chips used for GPS and AGPS and GLONASS. As is discussed already that PPS GPS used two way frequency at 1GHZ and 2.4GHZ accordingly which helps to get a FIX more quickly and accurately as well. We are working on different type of GPS devices like Garmin for Portable GPS and Numerix and ALAPL devices for fleet tracking , GPS Navigation for Cars which are some different sort of devices.
Summary is it's hardware dependable, some cell phones comes with GLONASS which are Russian based Satellites and AGPS (ASSISTED GPS helps to get Fast Fix and location accuracy clocked at newest frequency) and some phone comes with both AGPS and GLONASS while some chinese cell phones don't know maybe old devices/chips which were used while ago hence result is no GPS signals and less accuracy as compared to newest chips.
Basically GPS is purely American satellites while GLONASS is russian and China is also working and testing Beidou Satellites in test progress expected to complete in 2020 worldwide however it's available in china only for test purpose. Currently GPS and GLONASS is being used worldwide.
In short, in my practical life with GPS, GPS is more accurate as compared to GSM and more user friendly ... There are now devices available which can take Pictures (As camera is installed) which sends pictures and can be conncected with the engine as well for theft security. Day by day GPS is getting more advance and advance.