An interesting question. I'd say that one-and-only best registrar for all users simply does not exist.
There are so many things to consider:
Non-U.S. user is always more safe with non-U.S. registrar.
One should not forget that most complaints, udrps etc. are originated from the United States of America, it is very easy for such complainants (~$150 filling fee) to sue non-U.S. registrant in U.S. court with or without reason if the complainant wants to obtain a valuable domain which belongs to non-U.S. registrant, and (!) if the domain is registered with U.S.-based registrar. It is not happening too frequently because of greedy corporate lawyers who prefer to avoid such a cheap method, nothing else. However, if non-US domain owner registered his valuable domain name with non-US registrar, it would become somewhat more hard to sue them in the United States (of course there is an option to use Virginia court for com/net domains as verisign registry is located in Virginia, so the domain name is also technically located there, but it is another story).
The above does not apply to US-based domain owners, as they are already in mentioned country and can be easily sued regardless of registrars location.
For an enduser based outside U.S., I would recommend EasyDns registrar. They are Canadians, reasonably safe to use, easy control panel etc, and they would not shut the domain name down just because somebody emailed them asking to do so ("hello, we are London police, please disconnect the following domains"). There were such cases. Most registrars promptly complied - Indian Bigrock, many U.S.-based registrars, but not EasyDns. No order from Canadian court = no action.
For an enduser based inside U.S., I would recommend NameSilo of course, but if and only if the user is technically advanced. NameSilo has soo many cool professional features that an average enduser may be lost. A next development step of this no doubts the best U.S.-based registrar might be introducing two types of accounts/interfaces - simplified for an enduser and professional(current) for a domainer or reseller.
Uniregistry? Also an option, because of safe Cayman jurisdiction. I wish they could improve their marketing team though, I feel I still need some "psychological recovery" (or a lot of beer) after they sincerely promoted .xyz(!) on the 1st page and by email like the next big thing similar to bitcoin... And I never know what image will I see next time I visit uniregistry. Ok, at least there is no dancing Jean-Claude Van Damme (who was dancing on GoDaddy a few years ago for a couple of weeks or so).
GoDaddy? Please return Danica Patrick
. It is boring to see the same no-named guy with headphones, for many months, each time I'm going to login page. With a dedicated account manager (and only with a manager) GoDaddy is OK. Or with
@Joe Styler who is always here to help, thank you so much Joe for being a member of this forum