Alright so first let me say BoxBilling is great software for the price, but let me tell you why it should not be used in any production business bigger than small.
1. BoxBilling does not collect enough client data on sign up nor can you just search for your clients for fast finding during a chat.
2. I don't believe correct me here if I'm wrong, that BoxBilling stores the ip address on the clients info, this also isn't good for fixing problems in ssh.
3. BoxBilling also offers very limited payment gateways for on site credit card payments.
The Good Thing About BoxBilling Are:
1. Easy to integrate and use for anybody.
2. The price for unbranded is unbeatable.
3. It can be used in a smaller hosting business with great success.
The softwares that I like compared to WHMCS are ClientExec and Blesta, but Blesta has no Knowledgebase witch is a downside.
Blesta and ClientExec also integrate really well websites.