Internal company or domain registrar nameservers

Hi, Wondering if anyone can help, I have recently installed CPanel/WHM for the first time and I'm slowly getting my head around configuring and maintaining it, previously I was a user. We are hosting ourselves and have our own internal DMZ nameservers, should I be using these nameservers or the ones from our domain registrar? Currently using our own and all appears to be working fine but wasnt sure if this was correct practice. Any advice appreciated. Cheers