It's of course the benchmarks that are centered around browser tests, which are the most important and interesting to us; take a look at the iPhone 6 and 6 Plus scores:
http://www.gsmarena.com/apple_iphone_6_ ... 1142p5.php
The browser tests are the 2 tests at the bottom.
What is missing is the iPhone 5 with iOS 8; the one in the link uses iOS 7 - but I tested my iPhone 5 with iOS 8.0.2, to 12424 in the Kraken 1.1 test (using Safari), which is a nice improvement over the 14.171 for iOS 7 on the same device (lower is better), but still very far from the stellar performance of the new iPhone 6 devices.
So; I'm using my iPhone 5 as a test platform right now, as it marks the slowest performance people in general will encounter. Of course there are still a lot of 4s and 4 devices around, but as time goes by, they become more rare - and we can trust that an iPhone 5-ish performance, even for lowend smartphones, is indeed possible for us to aim for.
* It's worth noting that running the Kraken 1.1 on the latest Chrome for iOS (8.0.2), resulted in a freeze. o_O