ask yourself, do u want to jailbreak your i3gs? if yes then proceed to use redsnow or purplera1n to JB and install cydia.

Previously your i3gs 16gb form the state need to jailbreak n unlock before it can accept foreign sim, therefore u need cydia to install ultrasnow to unlock your i3gs 16GB. 
but your i3gs 32gb is officially unlocked so u do not need to jb n unlock in order to use it.... u can just insert any sim card and start using it.