Thanks Sebastian,
Here’s what I’ve noticed.
For big models like vgg and others probably the difference between DataLoader and No DataLoader is negligible.
Here are the results for vgg16.py on TitanX

And for vgg16_inmemory.py

But if I swap your vgg with just the small model I had before with just a couple of dense layers then, the results for vgg16_inmemory.py --> now just contains a couple of dense layers only.

And the results for vgg16.py --> now just a couple of dense layers.