Don't understand how is it possible to compare
Kamailio with the Acme Packet SBC. Just to give an example, the DoS mechanism available on the AP SBC can't be compared with any other solution available on the market. You will also have HMRs, SIP Routing options out-of-the-box (like time of the day routing, sip method based, cost based, traffic classification based, lb, trunk group, enum,lrt, multistage, route header based, redirect, etc etc) and infinite number of features that you will for sure miss if you plan on making that replacement.