I just got a new laptop today and when I saw the ssd it blew my mind. Most of my old drives are like the second from left and it's what I think of as a normal drive, buying a standard ssd still feels small to me. But look at that tiny thing to the right! It's the size of a postage stamp!
Assuming I managed to find the right specs (it is a Microscience hh-1050): The monster on the far left is from 1990, holds 40mb, read/write of 0.625mb/s, and weighs almost exactly 2kg. The baby on the far right I got in the mail today, holds 1tb, read/write of 5150mb/s, and weighs about 2.85 grams.
So we're looking at 25,000 times more storage, 8,240 times faster, and 1/700th the weight! And the one on the right is just 1tb, they make one that same model but 2tb. I can barely believe it exists even though I'm literally holding it in my hands.
Do manufacturers use the extra space for larger batteries, or just to make the product smaller overall?
Yes.
This is for desktop PC. But the correct answer is overall smaller because if you only had spinny drives a lot of small devices wouldn't be possible.