In 2015, We have conducted a few tests to compare the performance between SSD based web hosting and HDD based web hosting. We found –

In sequential read, SSD performed 5x (500%) better than HDD hosting
In sequential write, SSD performed 4x (400%) better than HDD hosting

If we use web server mode to test, in random read/write, the SSD storage performance and latency (i.e. responsiveness) is better than HDD ones

For test details, you may refer to here.