If you're on iOS it would make sense since Apple is only allowing it's own webkit as browser engine, forcing chromium and firefox to be disfigured versions of what they are on other systems.
When I was working more frontend (~1,5 years ago) no browser would cause more work and trouble for us than Safari on iOS (we didn't have to support IE9 and lower).
Nah I'm talking about Chrome and Firefox on Android. They are both worse than Safari on iOS.
Also I understand that Safari might've created some pain for you as a frontend developer, but frankly I don't care. I'm an end user and I only care about how fast and secure the browser is. And Safari wins there, it's not terrible by any measure for the end user.
Safari being faster on iOS might be more indicative of your iDevice's performance rather than Safari's (the A-series chips are quite fast). Without being able to run both browsers on the same hardware you can't really make an apples to apples comparison.
> Chrome and Firefox on Android. They are both worse than Safari on iOS
I realize that this is subjective, but Firefox Focus has been my preferred mobile browser, regardless of if I have Safari available, (iPad), or not, (Android). In fact having desktop addons on Android has been great.
That might be your personal impression but I don't share it.
Development wise it's not so much about our pain as about certain known bugs that went unfixed for up to 2+ years, similar goes for a range of CVEs (re:being secure).
Performances issues will be hard to estimate, as you can not compare safari to the others on the same phone, which means that you will not be able to correct for hardware and software stacks influences.
When I was working more frontend (~1,5 years ago) no browser would cause more work and trouble for us than Safari on iOS (we didn't have to support IE9 and lower).