Hi Vinay.
If you want to save time and make a Fast System copy with minimized/Zero Downtime in source system is better make an Backup/restore System copy.
If you can stop your source system is better make an R3load because in this method, your database will be reduce the size and you can start a new system cleanly.
Both method are valid and both method will guararantee a consistency system after finish.
And with both Methods you can change the SID without problem
.
regards.
Christopher Arias