I moved to Opera a few years ago because it performed better than other browsers when kept open for weeks on end. Its ram usage would often clock in at multiple gigabytes less than chrome or firefox over the same time frame even when keeping < 10 tabs open. It allows total customization of keyboard shortcuts and has been an excellent experience. Their iOS version has a built in ad-blocker which prompted me to switch on my phone as well.

Just this week i swapped to Firefix quantum to test the waters here. My initial reactions are fairly muted. It is almost an identical experience given my browsing and development habits. If anything, i would say i still prefer the speed of Opera's (well, Blink's) dev tools.