Png And Jpg Textures Performance

Png textures are usually 3-4 times bigger in size then .jpg textures(say both textures are 1024x1024), is using jpg textures better for gpu performance?

Not really, they get compressed internally to DDS, DXT, R8, etc
So All you are doing by importing JPG is creating pixelation/distortion before additional compression.
So all it results in is additional compression/detail loss.