in a program like this, it makes NO difference , whether i save as PNG or GIF ? (size?)

in a program like this, it makes NO difference
                               whether i save as PNG  or  GIF ?
                                  (is one smaller than the other?)
black= (0,0,0)
white= (255,255,255)  .............
from PIL import Image
from PIL import ImageDraw
def newImg():
     img = Image.new('RGB', (120, 120))
     for i in range(100):
        img.putpixel((10+i,10+i),   (red, black, white)[i%3])
     img.save('test.gif')
     return img