The best linux copy and backup method: Rsync vs cp

I need a method I can make a backup from my laptop. I used a USB HDD for that and linux prompt.

1. step: Make an initial copy of your data

So, after i mount my USB HDD I used first time the cp command of course.

cp -rpv /home/ /media/usb-hdd

2. step: You can keep up-to-date your backup with rsync

But from the second time I need to use rsync for faster copy and backup synchronization. If you are not a rsync person I have to say this tool is very cool. The fastest and best way. It copy only files that changed. So this is the secret why so fast. I use this command for backup my data to a Remote HDD:

rsync -av /home/ /media/usb-hdd/home/