Reasons why WINDOWS PHONE doesn't lag explained

Is WP still lacking something or were they sacrificed for performance?

1) Kernel-

WP updates it's processes and app processes continuously even when asleep. Don't get me wrong, even Android and iOS do that, but as far as I know, those mobile operating systems update only their main kernel and the hardware feeds. In this case, Android shuts down the services and information updates of the app, but the hardware is still on use though the device is a sleep.

That's why, if you wake a midrange Android phone, and quickly navigate through, you will notice the lag. Especially on Samsung TouchWiz phones.

2) Rendering priority-

Android does the rendering on main thread with normal priority LIKE WINDOWS. iOS does it with real time priority.

Now you relate which one WP belongs too.

3) Services-

iOS and Android have tons of services which aren't made to run when they want. Eg- Google Play Services

Those services keep wandering in the memory.

I several times noticed the following tag in my Nexus:

"The service was started by an app. Closing this service may cause the app to crash. (or) This service is triggered automatically by an app"

I'm sure even iOS does this in iOS 7. That's why iOS 7 lags especially on iPhone 4 and 4s (consider the hardware too).
However, in WP, the services are started when the OS or app requires some particular info.

4) UI-

Android has pretty much a complex UI with interactive notifications etc. Android also has widgets and other complete stuff like Google Cards which require services to run continuously, waking up the processor continuosly affecting the battery life.

WP has tiles and iOS has stack of icons which are simple to render.

Live tiles don't take much resources.

5) Multitasking-

Android's multitasking is shared on priority basis, 1st priority to the system apps and 2nd to the third party or basing on resource hungry. Open a couple of games and you will see that they consume about 60% of the RAM individually than 100% when running.

But WP and iOS hibernate the apps causing delay in the travel paths of the information. iOS doesn't have proper multitasking and WP hibernates the apps like in Windows 8+ PCs to save battery life and give some room to the OS.

Disadvantages-

However, WP is far behind, considering the services and multitasking.

In Android and iOS, the services are ran automatically, (refer #3) but in WP, they are triggered when they are needed, causing long waiting times. Now you know why apps take long time or they say "resuming/loading" especially on 512 MB RAM devices.

Android tried to improvize more by introducing "ART" (beta) runtime.

Eg- Weather.
In WP, when you tap on weather, it takes time to gather and load the info from bing.
However in Android, if permissions are set, Google Now updates it automatically. So if you open Google Now, the weather card is ready to show up.

Microsoft engineers wanted the OS to be lag free, but sacrificed few of 'em. Cannot blame them afterall.

P.S- I'm not against any OS.
 I put both pros and cons for each OS and tried it to make a fair comparison