ziphone used to downgrade your baseband to 3.9 without your consent when you click the one button solution. not a good thing to do as some functionalities on the new firmware might not be running well with 3.9 baseband. (ijailbreak that uses ziphone method did not even ask for downgrading the baseband) i had a bad experience with this...

winpwn or pwnage tool can let you choose which baseband you want to upgrade to btw, with winpwn u can use iphone 2.0 beta fw on you iphone (am using one now)

so for a safer method use winpwn.

not sure about iliberty+ since i never try before.

i did say the one button solution click 1 button an worry free? i dont think so. not sure how good is ziphone but i still prefer pwnage tool

iJailbreak (for mac) which is built using ziphone method doesnt let user to select to downgrade baseband (at least at the time i tried it)

right now i just use pwnage tool and just update it through itunes like normal iphone.