I have the same perception. It must have to do with the webView’s scrollView deceleration rate. Just ran this test, and 1) it confirms our suspicion and 2) suggests a fix.
I added a scrollView and a webView to my UI then logged the following:
NSLog(@"my scroll view's decel rate is %f", self.scrollView.decelerationRate);
NSLog(@"my web view's decel rate is %f", self.webView.scrollView.decelerationRate);
NSLog(@"normal is %f, fast is %f", UIScrollViewDecelerationRateNormal, UIScrollViewDecelerationRateFast);
The output confirms the guess about webView being more frictional:
my scroll view's decel rate is 0.998000
my web view's decel rate is 0.989324
normal is 0.998000, fast is 0.990000
And suggests a fix:
self.webView.scrollView.decelerationRate = UIScrollViewDecelerationRateNormal;