Both of them. Having a great name is what it's going to attract gamblers to your site, but you won't achieve anything if you have great marketing and perfect visual aids but your site is shit or doesn't work. So basically you need to get that balance.
What is the essence of marketing without good sites in the first place? I think for you to succeed in marketing and promotion, you need a good functioning website to achieve that, you need fast banners for the current promotions for customers to be able to swing them left and right without any difficulties.
If you have a good foundation, extensive marketing and an excellent reputation but a bad website, that is as good as making a bad reputation because customers would find it hard to deposit and withdraw and in the case of going offline, that's just as good as a dead place for people to come and play.