Using the same company for domain registration and for website hosting is potentially risky. Problems with hosting are not uncommon. You may not like their service and want to switch to another host. Your host may think you’re using too many resources and want you to upgrade to a more expensive plan. They may claim that you’ve violated the terms of service (TOS) you agreed to when you signed up for hosting. Most TOS agreements make the host the final judge on whether you’ve violated the terms.
Basically, if your web host has control over your domain as well as your website content, they’re in a position to dictate terms to you. They can freeze your account until you pay more money, or they can close your account. Without control of your domain, you could find your domain, website, and business completely shut down.
On the other hand, If you register your domain using a different company, you can switch hosts by changing the nameservers that are set in your domain account. Not only will this protect your domain in case of a hosting dispute, you’ll probably get better service when you use a domain registrar for registration and a web host for hosting.
If you host with your domain registrar, the biggest threat to your domain and business will probably be honest misunderstandings or mistakes, not a disreputable company. A client may do things with his website that unwittingly hurt other clients using the same server. If a client uses a $5/month shared hosting account to make a YouTube-like website, a host must take action to protect his other clients. Hosts can make honest mistakes as well. They receive a complaint that you’re a spammer and take action against you before checking the complaint thoroughly. They may think you haven’t paid when you have.
In summary, pick a web host other than your domain registrar to give yourself the best service and the best protection for your domain.