90% is close enough to twice as fast. With the gpu getting a 2 core bump probably more than twice as fast.Not considering that the A7 was twice as fast as the A6, which was twice as fast as the A5, which was in turn twice as fast as the A4.
The iPhone 5s was something like 8 times faster than the iPhone 4, and that was in the course of 3 years. 2 1/2 years later the iPhone 6s is only 90% faster than the 5s.
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Not according to the benchmarks.
https://browser.primatelabs.com/ios-benchmarks