Read the contract/TOS carefully if you go with one of these offers. Even if the host puts the domain in your domain, it still might be a total pain to get it from them once you cancel hosting. These are question I'd personally ask them 1) will you provide me with the domain authorization number? (which allows you to transfer the domain to another host after you cancel), and 2) Do I have the power to unlock and lock the domain (if you're not given this ability, they could keep your domain locked which will prevent any transfer request).

There might be other things I'm not thinking of here that you might need to know, but just find out what the terms out to be sure.

I personally host and register my own domain at the same place. I find it convenient since I can manage everything at one location.