Sandboxing: no inconvenience whatsoever (seems to me that everyone should do it). There's no difference browsing sandboxed vs non, except when sandboxed I never have to worry about clicking a link. Even non-shady links can be unsafe -- recently my friend linked me to a local car show. Turns out the page had just been hacked. I didn't have to wonder if anything happened to my machine.

No flash/java/etc: not an inconvenience, and it keeps the browser unbloated. I had Flash set to "Always Ask", but then Youtube started defaulting to Flash again instead of html5 (or am I crazy?), so I disabled flash. As for java, it's been years since there was an applet I wanted to use in the browser. There was a math applet I wanted to use, so I just downloaded the page source and compiled it myself (Java is a language I code in).

uMatrix: not an inconvenience for me, especially with my whitelist established. I don't visit new pages often, but most new ones display fine anyway since I default allow css & images. Other things being blocked means pages load faster (besides being a security measure).

My secure browsing, combined with my not running/installing shady things, is what allows me to never have malware and never bother with AV's (which imo are useless).

The only tangible inconvenience about my setup is that some of my privacy settings can occasionally break pages (eg disabling dom storage, though to date I've only identified one page broken by that). But I have another browser set to allow everything, for when there's a new page I want to work immediately.

Firefox stopped being good when Chrome came out and stopped being popular when chrome addons came out.

Chrome has a built-in sandbox

Also the best browser is [anything] in Linux.

So best option now? Made do with Chrome until now but the "disable our new crappy font rendering" option got removed and every single website now looks like arse as if I've increased my resolution hugely