My girlfriend has a 5s (16GB) which is getting towards completely full. She hasn't upgraded to iOS 9 yet. I just read that it is very slimmed down in comparison to iOS 8. Is there a recommended way to make the upgrade so that her phone comes out the other side with more space available? I realize this might sound like a naive question, I've just never actually owned an iPhone despite being a Mac user. I know I can plug it in and update via iTunes, but would it behoove me to reset the device with iOS 9 and do a sort of "audit" of apps? Or is that just extra work and just updating via iTunes will save space by default? Thanks.