It's always interesting what different players notice first because everyone seems to focus on something different. Some care about the selection of games, while others pay more attention to how quickly they can find what they want or whether the site feels comfortable to use. I usually end up judging a casino after a few sessions rather than the first visit because that's when the small details become more obvious. Even if two casinos offer similar games, the overall layout and how everything is organized can make them feel completely different. That's probably why discussions like this always have such varied answers.