the SSD is not the bottleneck, so even if they increased its speed 10 times it wouldn't have that much of an effect.
As for the rest:
(
https://www.notebookcheck.net/Intel-Iris-Plus-Graphics-650.190370.0.html)
The processor is also slightly faster, and they bumped up the 8GB 2133MHz LPDDR3 memory (from 1666MHz on the low end model, if I remember correctly).
So overall my guess is around 10-15% increase in performance.