Tell me please, if among you online slots players ?

  Hi guys)
I am reaching out to you for a reason that is important to me.
I recently changed my profession and I need an opinion and advice from the outside, especially from online casino players!
At the moment I am testing different gaming sites. From roulette to slots without downloading for real money. Perhaps if you are an active user of YouTube, you can find my reviews there. 
The bottom line is that I do a compilation: the worst and best online casinos.  I am currently processing what I think is the best platform at ........ . These slots have conquered the Canadian players, and in general, many countries, the popularity is growing, the reviews are more and more. 
Tell me please, if among you online slots players ? What do you pay attention to when choosing this portal?