They all provide the same result. The only difference is that My3G lets you specify 3G use for any app that is restricted to wi-fi only(there aren't many) whereas Facebreak is specifically for that one specific application.
3gvenice works on iPhone 4 v5.0.1 flawlessly but I've yet to try it on v5.1.1 and it's specifically for FaceTime,may be try it tomorrow as just upgraded to v5.1.1. If anyone else has tried it please let me know, thanks.
Cydia
Manage
Sources
Edit
Add http://apps.iphoneislam.com/
Return to cydia
Now in manage/sources just open iPhone islam source page and find "Faceit-3g x.x.x