Some informal testing reveals that if you’re still rocking an old iPhone, you should probably upgrade to iOS 9.2.1.

iApple Bytes put three different models of older iPhones — the 4s, 5 and 5s — up against each other in a variety of tests designed to see which of them was faster starting up, using apps and running Siri, Apple’s digital assistant. Half were running the brand-new iOS 9.2.1, which arrived yesterday, and half were still on iOS 8.4.1, which has been around since August 2015.

You can see their results below in iApple Bytes’ series of videos.

The first public update for iOS 9 this year has finally arrived in the form of iOS 9.2.1, which was made available to all iPhone, iPad and iPod touch users this morning.