Customization is for Most Network Providers Like "rogers wireless", "AT&T" so they can prevent the phone from using Mp3 as ringtones or make it so you have to download there product in order to have ringtones. Antoher Reason for customization is to have you use their software. The Filesystem isn't much different. Customization is pretty much the same if it's from the phones original software. I hope you get what i mean