Is it one that you just use and works just fine? Or one that has proven to be reliable and responsible if they do a mistake and only want to satisfy you as a customer?
I’ve been using namesilo for years without issue
AWS (Route53 specifically). Not common but my personal lab runs on AWS so it’s nice to have a place for everything.
I currently renew my domains on namecheap and manage the records on cloudflare. Namecheap’s web interface is trash (doesn’t work in Firefox for no reason) and I dread every time I have to touch it. I’m currently considering just moving the registrations to cloudflare too.
Leave the registration with NC and move the DNS to cloudflare. You should separate the two functions anyway so you have fallback ability for both. If the DNS is borked, you can go back to the registrar and change name servers, and if the registrar is down, it doesn’t affect your DNS.
Currently namecheap, but I was pretty mad to see that API access (for ACME DNS record auth, which I need to prevent downtime) was not available due to my yearly plan being too cheap (?!). You need to spend at least 50$ per months or have at least 20 domains for no good reason.
The best solution seems to acquire the domain using namecheap and then transfer name servers to a better service.
I usually pick whoever has the best deal when I want to register a domain.