For me, it's always the reputation. Everything stems from it so you can't really go wrong, they wouldn't have a good rep if they are cheating their customers or if they are being rude to them right? So I am pretty sure that reputation would be the greatest indicator that something is right with that casino that we are choosing.
Casinos with a good reputation often create conflicts with their customers, which goes against that customer. Now if a good reputable casino doesn't have enough games then it may not be your choice. So taking the opinion of the community can be a good way to choose a casino. Because if an experienced player gives a good review about a casino, then new players are interested in doing more research about it. A casino's reputation will be good as long as they work honestly with their customers.