9.1 is actually better than 9.0, so you should upgrade. I told my client who told me about performance issues to upgrade to 9.1 to see if it's better, and it wa

9.1 is actually better than 9.0, so you should upgrade. I told my client who told me about performance issues to upgrade to 9.1 to see if it's better, and it was, but just a little bit. We were then stunned to discover that his old iphone 5 ( not even 5s) performed better on ios 8. I knew before that ios 9 had huge graphical performances issues, but i didn't know it was that bad. Since it's graphical, i have another theory which is that johnny ive asked to add invisible gui effects a little bit everywhere in the OS, and that it baddly affected the overall performance of the OS.