they are different
MOST of them are things that will NEVER be allowed on the appstore
majority of cydia apps allow you to do something that should have already been there, not an actual app
they make the iphone what it should have been
and most of the stuff that comes out on cydia eventually becomes part of the stock firmware from apple (landscape texting, tethering, video, mms, and the appstore itself all came from cydia)
if you want to get the most out of your iphone, jailbreak
if you wanna get ALL the appstore apps for free (with a hack that is installed thru cydia
see how that works) then jailbreak and nstall a free app from itunes then install appsync
WHATEVER YOU DECIDE!
DO NOT post questions on this site or any other UNTIL AFTER you have searched for the same question on here and google
99.99999999999999999999999999999% of the time, your question has already been answered
dont slow down our site with a bunch of stuff that is already posted.