Judging by the answers, you mean registrar. The registry is the place that administers the register of domains within a TLD (like .se or .mobi) and for some reason doesn’t let you order domains unless you want to become a registrar first

I don’t know which registry is the best but I can tell you about the worst. My registrar was also not amused by the mess that is AFNIC (twice now, concerning different domain names, and I don’t have many domains so if I already had multiple problems…). They sit in Paris and operate the TLDs of former colonies