I sadly dumped Opera for a while. Opera 27.0 is different - but you need to download it (repos are out of date).
Since a sketchy start with Netscape in the late 90's I moved to Bangkok and started using Windows '98 in netshops.
My early discoveries of tabbed browsers led me to carry installers.
Firefox was wonderful, as was Opera. Opera took over as the easiest and best to use quite quickly.
Annoyingly (as I wanted to tout Opera as being the best thing since sliced bread...) the mouse gestures available in Opera soon found albeit less capable options in Firefox.
If you don't have 'Easystroke' installed, then you are effectively crippled. In addition to all of the usual methods/shortcuts etc, my entire desktop responds to mouse gestures. I can manage very happily with my Logitech k400r (decent trackpad, enough media keys to make it work as my remote control when I'm cooking/outside smoking) - but when my mouse comes into reach I can do a lot more magic.
Still I remember they originated with Opera browser. After the startup and rapid rise of Google Chrome I found sadly that Opera was lacking. Opting for a dark theme (BlackMATE - even on Cinnamon desktop - is by far the best dark theme for controls IMO) Opera couldn't display fonts!!! White on white url bar.... so I didn't even install it with Cinnamon 17.1 until last week.
Chrome is nice - but has severe issues. Google has very good reasons (and states that it does indeed LOOK at data) to use your data. For this reason I'd choose Chromium over Chrome. In benchmarks (fair ones) Chromium browsers are maybe 5% faster (basically the same - feels fast) and certainly not like the old Bentley Firefox (cruising internet rather than surfing... with your lovely Downloadhelper essential to throw Youtube video's into a nice download folder in .mp4 720p or better for viewing on the HDTV later).
The point I'm trying to make is that you should NOT really choose. The loss of any browser is a loss to the whole community. I try to support Chromium, Opera, and Firefox equally.
Firefox is my weapon of choice for:
1. Plex Media Manager. I haven't tried it with Opera, but I know it has an issue in Chromium - adjust settings, press save and see 'Error Saving Preferences' appear. Who cares why, just use Firefox.
2. Browsing and downloading. Downloadhelper - wow, go to a page with links and images and you can leech a few hundred images into a folder of your choice. Of course, at times, other Firefox plugins make it invaluable... but sometimes they make it remind me of Windows. Start it up and it wants you to wait while it checks it's plugins and update stuff... and then other times the plugins have brought it to a standstill in the past.
3. I had an issue with tab switching (Chromium lets you mouseover and roll the mousewheel, Opera does not... but Cinnamon gives us CTRL-TAB and CTRL-SH-TAB for this... Easystroke lets me map this to Right Mouse Button + mousewheel Up and Down - removing any advantage in that department. Thanks to Chromium for that idea - now my entire desktop works that way.
Easystroke is a great equaliser... L closes tabs, draw the L from the bottom and the tabs come back... draw a lightning stroke and windows minimise, draw an inverted 7 and they maximise, arrows make them tile into corners/halves. Write number 1/2 to go to that workspace... and mapping CTRL and ALT to my buttons 7 and 8 means I can do lots of extra window manager jobs (resize, zoom in window, zoom desktop etc) without having to use mouse + keyboard.
Now my advice is to keep Firefox for doing what you need to do (when you aren't sure how to do it in Opera or Chromium), and for using it's add-ons, and because it is historically a pig/great browser/vital.
Use Chromium and Opera. Learn how they work. Read about their shortcuts. Use Easystroke to make them all work the same way under your mouse.
I find myself using Opera more than Chromium right now for 'browsing'. Though for regular browsing I launch from 'application shortcuts' in a Docky dock bar which is hidden on my left side of the screen... so I use Chromium for those.
Interestingly, Lastpass installs nicely on all three browsers - so I can at any time click the icon and directly open and log in to them (with lovely obscure passwords like 'wYRi8nEsBPAxCSsY399OmGoW').
Truly there is less and less reason to eliminate any one of these three. There has always been a good reason to support all three.