The update has bug fixes, features and performance improvements on the phone. It new update will let you back up videos from your conversations.
Updates to Android and Window Phone are very frequent, iOS was clearly ignored, since this updates will bring a lot of hope for iOS users.
Now, iOS users can also reduce their data usage for voice calls, when WhatsApp is used for making voice calls. Do remember that the quality of call will drop so you should not blame it on WhatsApp.
These settings can be found in SETTINGS–> CHATs and CALLs. However, this update was rolled-out few days back for Android on web, users were supposed to download and install in their device, but an update directly to phone is not yet arrived.
WhatsApp has rolled-out an another convenient update as now you can mark a chat as Unread or you can swipe them to archive. This is very convenient during annoying group chats.
A swipe to right side will mark chats as read or unread. You can also customize notifications for particular chats.