Seems the new Samsung Galaxy S5 and The HTC One M8 are the current leaders. Both have similar specs, just don't get an iphone.
iPhone isn't high end.
iPhone 5: Dual-core 1.3 GHz, 8MP cam, 1 GB RAM,
Samsung S4: Quad-core 2.3 GHz, 13MP cam, 2 GB RAM
Technically, an iPhone is comparable to a cheap China Mobile in the 100~200 EUR price range.
Check out their Geekbench score. http://www.macworld.com/article/2049270/benchmarks-iphone-5s-lives-up-to-the-hype.html
Iphone 5S 
+1
Those benchmarks makes no sense, iPhone and Android are way too different at OS level to can be compared like that as even if the app has the same label it has a different code and approach.
Still, one of the biggest advantage of iOS when it comes to performance was to trash Java and Flash junk. Android ditched Flash junk, but it's mostly Java. Java should actually change their motto from "Over 300 billion devices uses Java" to "Over 300 billion devices crashes with Java" (or go dead slow).