Q:

Difference between ways of rooting device

Possible Duplicate:
Why can't the su binary simply be copied (techical response please) 

What is the difference between flashing device with root ROM and simple pushing su utility to device using adb without flashing it?
If I don't need to launch applications which need a root functionality, but just need to relocate some files in android file system, using su, do I need to flash my device?

A:

In my understanding, the end result is the same in both cases, it's just the rooting methods that differ. Some devices have vulnerabilities that can be exploited in order to push the su binary to the device via adb (example), but these do not exist in all devices. This is why flashing is required sometimes.
TL;DR: It depends on your device.

