ALL GPS are affected by climatic conditions, how many satellites are visible from your current location (the constellation of satellites does move around leaving fewer on your side of the planet sometimes) and so on. To say "some older ones" is incorrect. Yes new or expensive ones may be better designed, but you can't overcome the basic limitations of the GPS system, its a very weak signal that penetrates badly and reflects around and on the civilian band is affected to varying degrees by atmospheric effects.
