I know that's just one data point, but I'm super-sceptical given all of the misinformation that's been floating around about this topic.
Have not benchmarked it but it was only slow for a week or two after upgrading to iOS 11 and seems fine now. Did not notice slowdowns when using iOS 10 (which was when throttling was introduced)
Apparently general sluggishness is not caused by the battery, but by some rogue iOS system process (which a reset fixes).
https://daringfireball.net/linked/2017/12/22/glenn-iphone-sl...
if "everything" is slow on your iPhone, it’s probably not this issue related to older batteries. A full backup and restore is a pain in the ass, but it’s worth trying. There are clearly some bugs in iOS 11 that triggered such problems in far too many devices.
http://mglenn.com/blog/2017/12/22/apples-bungled-battery-fea...
Ever since iOS 11 came out I had experienced a significant performance issue on my iPhone 6S. Animations and transitions were slow, app loading was noticeably and unbearably slower than iOS 10 and my battery was draining faster. Many rumours swirled that others were experiencing this but not all. […]
Then several weeks ago a Reddit conversation started spreading online that presented possible evidence Apple was reducing the performance of their iOS and possibly laptops when the battery life was sufficiently degraded. That day I decided to test the theory by getting my battery replaced at the Apple Store.
[…] After I confirmed with her that I was not using it that heavily and the battery setting statistics also didn’t show an application using a large percentage of the battery she suggested a rogue system process that somehow persisted through upgrades and restarts.
She also let me know that my battery was at 83% health and that Apple won’t even do a replacement unless it’s below 80%.
So I went home and immediately did a local backup, wipe and restore. And voila! Performance issues were gone.
The test scenario was not described, this is only one sample which could have been selected and the source is not credible.
After 12 months of heavy daily usage on my 6s, I'm seeing 87% battery capacity left as an example after over 312 cycles. I am also seeing the same benchmark as the day I got it.