WHMCS is widely used and most reliable. If it wasn't that good, people would have not been using it for that long
I will highly recommend you give it a go if you are in the hosting industry. It happens to be the most popular panel for billing management and also hosting automation. I remember the tough time when billing systems were not that automated and we had to manually charge everyone. But with such inventions, things have become quite simpler for us. Whether you are a host or a domain registrar WHMCS is definitely the way to go.I'm wondering whether people can use Facebook for selling their services direct? Like instead of getting WHMCS? And use another way to do the accounting part of the Web service. It's just an idea that occurred to me while I was checking through a YouTube Tutorial a couple of weeks ago of how to do selling from one's Facebook Web page. Not only is WHMCS exorbitantly expensive, but it's like a dinosaur. I haven't had a perfect experience with it yet. I get it as it is good at getting things together under one roof, but maybe it's time to disassemble all of it and see how one can run it from more than one platform without need for WHMCS.