IMHO more channels improve calculation accuracy. Reduce likelihood of losing a 3D fix even in urban canyons and in dense forests.
While a minimum of four receiving channels is necessary for parallel processing, the extra ones are used to keep track of whatever satellites are in view and to be ready to replace one of the four being used, additionally more parallel channels=faster fix and less battery consumption.
Phones or devices with wireless capabilities are be able to get a position by supplementing with information from Cell nework towers and nearby wireless networks too.(Assisted GPS)