I am working on an android application that uploads a file to my server and then gets a string response. The String requires modification before presenting to the user.Should the modification be done on the server or the phone...Which is faster?
Server is something you control. If it's slow, upgrade it. But you cannot control devices and there are plethora of them, some are high-end some are low-end. So basically you cannot expect any processing to be fast on the device side because their performance is not uniform.
Having said that, I would suggest moving as much processing as possible to server side. A good app is light but rich. Just like Google. It's just a text field on client but behind the screen it is powered by thousands of servers.