I won't consider these four gambling sites as the 'best' . Making your top choice is subjective of course. Well, personally, I haven't into these gambling sites but I have heard some things about them this past months. I'll just speak in general. If you are finding a good gambling site or let's say, which would be the best for you; make a standard which would satisfy you. Why? Most of the gambling sites are having the same thing nowadays. One gambling site have offered promotions, and other have done such thing too. There are many gambling sites within a gambling site, other sites have made the number of their games, bigger. To sum it up, they will seem to be the same , really. So in order to choose your 'best' make your own standard on choosing and make it your basis. You have mentioned four gambling sites, then make a standard and check if these sites have passed your standards.
This is what I have learned before when I am still finding a gambling site to stay for years. Luckily, there's one which have satisfied my criteria and I am now months already in this gambling site.