Few reasons:

1. Firefox crashes would take down the entire browser, not just specific tab

2. I often load a lot of tweets in Twitter.com tab (back 4 hours). This causes Firefox to freeze.

3. If I refresh the slow tab, I watch memory not being clean and still stay there for several minutes. Chrome clears memory very quickly.

4. Why is the space around address bar so large? They are like 15 px top and bottom. What a waste.

5. Postman is only Chrome

6. Chrome Dev Tools is 10x better

I have no complain about CSS rendering issues or anything like that. It's mainly just performance. Also I tend to use Firefox in the firewall because the Proxy feature works quite well to connect to my internal lab.