As far as my previous experience is concerned, I would vote for https://domainia.com/register as the best one in terms of domain name registrar. I have registered domain names for the website of my clients from several places. But the service and the ease that I got from this place is way better than the others. Yes, indeed you will find differences in the offered price range for the same domain at different places, so pick your registrar wisely after comparing all the aspects.
GoDaddy and Hostgator provides excellent webhosting services and you can buy a domain name from their website itself.
GoDaddy is not the way to go, ask your web developer friends. In S.A. Hetzner Hosting is the way to go!
I use GoDaddy and they offer Value Added services and an easy interace.
I prefer to keep domain names separate from the hosting company that will house the website. It makes it much easier, if you ever have to switch hosts. I would suggest using GoDaddy for the domain name. They have good prices, and their control panel allows you to easily manage any names you have with them. I would then choose a hosting company such as HostGator, Web.com, Bluehost, etc., based on the site you need to build and the features you'll need from the hosting company. I hope this helps.
I have found GoDaddy for domain names and HostGator for hosting is a good combination for WordPress sites. I do not recommend buying multiple domain names. The exception might be a large company protecting a copyright.
GoDaddy! Of course if you want to buy just the domain name (www.example.com) you could buy it anywhere, because there is a minor price difference everywhere. But you never stop at only the domain, do you? (Unless you are in the business of buying domains that are likely to be in demand in the future) You always need an ecosystem to go with it. I recommend GoDaddy because of the ecosystem they provide and the customer friendliness of their service.
A Hosting provider offer free domain registration when you host your web site with them.