Both!

 The name of your website should be easy to remember so that whenever user want to gamble he/she will revisit to your website. And if the name of your website/domain name isn't easy to remember, then your users will forget your website name as soon as they log out from your website, and the next time he will go to that website which he/she remembers. Therefore, an easy-to-remember domain name is very important in my opinion.

The functionality is what makes you different from others.
I mean If you provide more features than your competitors, then you'll have the upper hand over your competitors and People will be impressed with your feature list and they would like to play again.