Which SIP stack/library is best for iOS?

Which SIP stack/library is best for iOS?

I am writing a VoIP/SIP dialer client for iPhone. But i am very confused
about which SIP stack should i use. I have searched all over the internet
and found about 6-7 SIP library which can be used for iOS. I have got the
following...
(Most used. Open source C-based SIP stack. Could be good if we want to go
low-level) http://www.pjsip.org/
(Not bad, updating continuously) https://code.google.com/p/idoubs/ ||
https://code.google.com/p/idoubs/wiki/Building_iDoubs_v2_x
(Not bad but hasn't been updated for a long time. Seems to be the default
option. Objective-c codebase with existing UI, It uses PJSIP stack.)
https://code.google.com/p/siphon/
(appears less mature than Siphon.) https://github.com/pzion/miumiu
(Another Linux-oriented option. Rough UI but the audio engine seems good.)
https://www.linphone.org/eng/linphone/news/linphone-for-iphone.html
(Couldn't understand.) http://sofia-sip.sourceforge.net/ ||
http://sourceforge.net/projects/sofia-sip/
So can someone please suggest me about which SIP library would be best for
iOS ? I will use G729 codec.