what makes one domain registrar better than the next?

[Biggy]

I never understood this other than the fact stability is very important, so a company doesn't go under and you don't lose your domains. The other issue is price. I personally use Domain Name Systems just because I have been using them for a long time, they are reasonable priced, and I loved their expired domain email newsletters when they came.

Is there anything else other than price and stability. Any service factors I am overlooking and not taking into account that I should?