In Firefox you cannot choose the folder to save files to, which is something I absolutely need because I mostly download porn but once in a while I have non-porn and these two must be in different folders.

Chrome doesn't support text reflow on zoom. I don't even have a comment because this makes it literally impossible to use desktop view which usually provides better experience.

I'm not even a power user. These features are IMO extremely basic things. Opera's built-in VPN is nice for browsing Twitter but that's an extra I could live without.