What is best option if money is not the problem?

Developing our own infrastructure using Kamailio and other open source packages to act as SBC and switch or buy a commercial solution like GenBand/Sonus/Sansay.

We are looking for high performance with scalability to handle thousands of call setups per second over the period of few years.

I have no idea on how/if can kamailio outperform commercial solutions or not.

Advantage of using kamailio is flexibility and possibility of customization as per requirement,

I am new to this list so please advise if this is not a valid question to be asked here.