I don't wish to throw gasoline on the fire here, but someone on another thread posted a link to a review by Anandtech. It is the first of any direct comparisons I recall seeing, and it does kind of back up what I've said that I don't think Android would perform worse than WP on the same hardware. Of course it is not exactly the same hardware, but comparing the 640 to the Moto G and Moto E, which have the similar specs, Android was at least as good if not better in most performance tests, including the browser. It was also comparable in battery life, and better in standby time. In any case, it's a good read.
The Microsoft Lumia 640 Review
It is a multi page review, but the link takes you to the system performance part of the review.
Let me start this by saying I am not a ****** of anything, and have owned a lot of Android phones. My main line is a s6 in fact.
This said, when it comes to Windows phone, hardware stats and apparently benchmarks are meaningless. I own a lumia 640 as my business phone, and it is very fluid, very consistent, and fast at everything except loading non ms apps.
When my s6 is working properly and not lagging, yes, it's stupid fast and nothing can touch it, including the nexus 6 I recently sold. However, key word is when. It randomly gets laggy, stuttery, janky. It's running 5.1.1.
Every time I pick up my 640 I know exactly what I'm going to get. The s6 is a crap shoot. Sometimes it's a beast. Sometimes it's a laggy pile of crap.
Btw, I don't see some of the complaints in that review. Stutter when pulling down the notification shade? My 640 definitely does not do that.
Android 4.4.4 was outstanding. 5.anything is like Vista or ME. It's just terrible and can trip up the s6's silicon which is ridiculous.
Random note: I'd buy a s6 running wp10 in a heartbeat. It's an incredible piece of hardware. The screen and camera tech are both absurd. Too bad the software lets it down.