Below is a chart I made comparing many key features. Please don't confuse YES and NO with an endorsement of a feature or lack thereof. These are all three great tools that offer a lot of cool teacher options. Which one you choose may come down to what you are trying to do and which one you personally like the best.
A few things worth mentioning:
I didn't know Kahoot had the option of scrambling questions and letting students move at their own pace, but according to their FAQs, they do. I also didn't know why they have the questions and answers on two different screens, but when I read about why, it made a lot of sense.
I just recently looked again at Socrative and I was really impressed at the changes they have made. The interface looks cleaner and more user-friendly now. I love the exit ticket and instant question options.
At PD I delivered in May and June, many teachers responded positively to Quizizz. This is the only one of the three you can try without an account and it has hilarious memes that are automatically delivered (if you select that as an option) when students get the right and wrong answers. There is a pop-up for live chat with the developers or to give feedback. That is a nice touch.
In short, try at least one of these with your students. You'll be glad you did.