Launching WP Apps takes more time than Android apps

I recently moved over to Windows Phone from Android, This is my only gripe. Launching apps like what's app takes almost 5-10 seconds on Windows Phones while it takes just 1-2 seconds on iOS and Android phones! I really can't understand why.

All the native apps on WP open instantly, but not third party apps. This is such a pain.

and I know there have already been discussions about Fast Resume. Microsoft needs to rake this seriously. They must make this a necessity before allowing an app to be published in the store, and also send notices to devs of app that have been already published to include this fast resume feature.

Really, The OS is fast, smooth and when apps open and resume so late, it sucks. Even a low end Android phone with single core processor and 512MB of RAM open what's app instantly.