It depends.
I can imagine next scenarios:
1. Under SIP trunks you mean calls from your provider to you
A) In case your provider can send calls to you - then you can use Kamailio, accepting all calls from your provider - based on IP.
B) In case your provider expects registration from your system - then, at least I - dont know how to do only with Kamailio - Asterisk can register easily to every provider.
2. Under SIP trunks you mean calls from you to World through your provider.
A) Your provider can accept all calls from you based on IP - Kamailio can directly forward calls to your provider.
B) Your provider expects authentication - then again I dont know how this can be done through Kamailio, but Asterisk can do it easily.
My suggestion is - you can use Kamailio for registration of users and load balancing, and asterisk servers for everything else.