CSIPSimple vs Zoiper

10
CSIPSimple
Native sip app for android device. SIP for calls and instant messages. Android integration with rewriting and filtering rules. Echo cancellation (with various backends : webRTC, speex, simple).
20
Zoiper
Zoiper, the free softphone to make VoIP calls through your PBX or favorite SIP provider. Available for iPhone, Android, WP8, windows, mac and linux.