I used Firefox for years, really liked it. Except for the constant pop-ups trying to get me to upgrade to the pay version, and which eventually became so annoying I was driven to look for a new browser.
I switched to Opera and never looked back. It's performed flawlessly, has a small footprint, great features, and best of all I NEVER see an advertisement. I love the 'Speed Dial' format, where I have the icons for my most used sites lined up. I can't say enough about this great little browser.
Recently Opera was bought out by a Chinese company. I'm once again looking for a new browser.
I've been hearing good things about Vivaldi, I may check into that.