I suppose a lot of it depends on your needs. For us, we run internal DNS servers for all the VMs we have running; mostly for software development and monitoring. It makes sense for us to do so as we have mostly Macs (and my Linux workstation) that work better using DNS. Had we been a mostly Windows shop, we'd likely use NetBIOS internally with some Dynamic DNS for
We also have external DNS servers for our cloud based servers, web servers primarily. We could have stuck with Network Solutions (our Domain Registrar) for DNS, but we have a LOT of domains across the globe and we prefer handling them ourselves. Management can be a bit of a headache at time, but it's worth it, IMHO.