As a “user” I prefer new windows if the website I’m currently on has more information I may want to view. But I prefer to right-click and make my own decision on that.
As a developer, i follow that pattern.
However, as an affiliate, I probably only have one chance to convert a player. So if they are going to an external partner site, or to a casino I have linked to, it’s a new window. If it’s an internal link, or a link to one of my other sites, then usually the same window.