Safari Technology Preview.
I used Chrome when I had a Windows laptop, but I was basically driven to Mac by the car-crash that was Windows 8 when I needed to get something newer that didn't heat up to the temperature of the Sun when running YouTube. I have an iPhone as well so Safari makes sense because of all the syncing between iOS and MacOS. Even without Chrome being a power suck on desktop, the fact that everything on iOS has to run on the same underlying architecture as Safari means there's just no point using anything else.
As to why I have the Technology Preview on my Mac? Its got a cool purple icon and there's absolutely no instability so why not be slightly ahead on updates?
Also, I use DuckDuckGo as my search engine to avoid the Google tracking. They have nice products but I tend to try to evade their ecosystem as much as possible, although a lot of group work at university tended to be on Docs and there is no substitute for YouTube, or Google Scholar when it comes to academic work.
EDIT: Because the British government is technologically backwards to go along with their 19th century social policies, I have to use Google Chrome to access my student finance. I have a browser just for one website, because for some reason they can't make their site compatible with a product from one of the most valuable and visible companies on the planet.