First thing I see is "CAN I WITHDRAW MY WINNINGS WITHOUT ANY HASSEL?" and then check KYC rules and lastly this might be a vey unpopular opinion but I like to see the UI of website because if i am willing to loss my money in there atleast make it visually appealing so it doesn't look so bad after all.
UI is not a big matter. almost every casino site try to use a better UI to make there site easy to use and understand the process and also for attract the gamblers. also KYC now is not any big issue Because if you can trust any site and deposit there without any worrying then why you should worry about KYC verification? i think the important matter is quick deposit & withdrawal and also a better community support, unique feature and attractive bonus. we gamble for fun so if we get some attractive bonus from casino site then it will more fun for us to gamble long time