Looks like the earpiece speaker is upside down in the photo of Step 9. It has springy copper contacts that align with the lower end (home button side) of the circuit board in the cover assembly. I referenced this photo when putting the speaker in a replacement mid frame, and the speaker did not work. Turning the speaker around did fix it.
There isn't much difference in volume. The new model is just a few cubic inches smaller, and it contains the power supply now.
The old model can comfortably be laying on its side, saving desk space. I wonder how it would work with the new thinner case? I like the looks of the new design though.