I read some code on the Vgg16 and I have some questions please. In some code I notice that they use the outputs like this :

vgg = VGG19(weights="imagenet",include_top=False, input_shape=hr_shape)
 return Model(inputs=vgg.inputs, outputs=vgg.layers[10].output)

Or:

output_layer = vgg.get_layer('block4_conv3').output

I am confused about what determines the correct choice if I use the outputs of layers[10] or block4_conv3 ?

Thank you in advance.