iOS 9 has been out for a while now and more than half of all Apple users on compatible devices have it installed. Although the new features on the latest version are pleasing, users have reported that the upgrade from iOS 8.4.1 to iOS 9 have slowed down their devices.

Aside from the latest iPhone 6s and 6s Plus and last year's iPhone 6 and 6 Plus, iOS 9 is also compatible with the iPhone 5, 5s and 4s. Needless to say, earlier models are more significantly affected compared to the newer ones that are equipped with better SoCs.

"Is this happenning only to me? After I had updated my iPhone 5s to iOS 9, it got slower a lot lot lot lot. There is nothing about being smooth in iOS 9. Control center, notifications center, spotlight search, animations," complained MOmeriz, an iPhone 5s user and Apple's online community member. "They all just bug a lot! iOS 8.4.1 was waaaaaaaay faster than iOS 9. iPhone 5s feels like iPhone 4 with iOS 7 now."

"I had the same problem with iPhone 5s. Performance got worse significantly," confirmed gaud1um, a member of the same community.

While a lot complained about iOS 9, some got irritated that the same thing happened with the other iOS releases in the recent years.

"I upgraded my iPhone 5 from iOS 6 to iOS 7. Everything slowed way down! Lots of people were complaining then too," detailed highland99. "Why is this always the case with your updates Apple?!"

An Apple-dedicated YouTube channel, EverythingApplePro, features a video containing a comparison of the iPhone's performance on iOS 9 and iOS 8.4.1. The devices tested involved the iPhone 4s, 5 and 5s, as well as the iPhone 6 Plus.

Using two of each device, which were both freshly restored to factory settings, one running on 8.4.1 and the other on iOS 9, tests involving boot time, application launch time, Wi-Fi and browser performances were conducted. Benchmarks to put figures on the SOCs' single-core and multi-core performance were done through Geekbench 3.

Boot Time

Put side by side, the iPhone 4s running on iOS 8.4.1 booted 8 seconds faster than the one that had iOS 9 in it. On the iPhone 5, however, iOS 9 booted half a second faster than iOS 8.4.1.

The iPhone 5s is where iOS 9 showed a significant lead over the 8.4.1, beating the older version by about three seconds.

App Launch Time

Several basic apps such as the App Store, Maps and iTunes were used to test and compare the app launch times. On the tested devices, the ones running on iOS 8.4.1 launched the apps faster than those on iOS 9, except on the iPhone 5, which loaded the App Store faster. The same results extend to the iPhone 6 where the one running on iOS 8.4.1 is faster than the other on iOS 9.

Wi-Fi

Based on the results shown in the video, Wi-Fi connectivity improves with iOS 9 installation. Speedtest.net results shows higher download speeds when running on the latest iOS version.

Browser Test

HTML 5 Test was used to compare how well each iOS version supported HTML 5. On every device, iOS 9 managed to win, by a slight difference, over the 8.4.1

Geekbench 3 Benchmarks

Benchmarks using Geekbench 3 are consistent with the results of the boot time and the application launch time tests. On the iPhone 4s, 5s and even the iPhone 6, devices running on iOS 8.4.1 edge out those on iOS 9 on both single-core and multi-core performance. The scores were tied for the iPhone 5.

Based on the results, it's safe to declare that iOS 9 does slow down the device and degrades usability. However, it also does not come without rewards. As observed, both Wi-Fi connectivity and browser support have improved with iOS 9.

At the end of the day, it boils down to whether or not the user is willing to trade off a little snappiness and responsiveness for new features.