Check local ports at the location, 30 sec drop means NAT/SIP ALG/Firewall
IndependentAngle3775
Asterisk is way more user-friendly and a good starting point. It all really depends on what your goal is. It is very stable if compiled correctly.
Kamalio is a great robust load balancer and is widely used for this exact purpose. Originally it didn't even have the RTP module and was handling SIP signaling only.
The biggest hit in terms of productivity comes from handling RTP traffic and transcoding. That's pretty much why one Kamalio can service multiple Asterisks.
Kamalio is far from being user-friendly and is usually used by service providers as a proxy/session border controller rather than a PBX. Unless you are planning on using it as a proxy there will be no real benefit over more user-centered PBXs. Since you were trying to find a GUI solution for Kamalio, my guess is that PBX is what you actually looking for.
Help - only law enforcement can help with getting needed info from providers
Guidance - block these 5 beyond comprehension traumatic numbers and find your peace
Check local ports at the location, 30 sec drop means NAT/SIP ALG/Firewall