The iOS version for iPhone, iPad and iPod sometimes lags behind the Android one due to the App Store release process being more complex. However it eventually catches up, as is the case with the latest release, which includes all the features and bug fixes from the past few months.
In particular a feature that's been needed for a while - the ability to open resources (eg. PDF files or other attachments) in external viewers. That means all that's available in desktop - notes and attachments - is now also fully available on mobile, making the app much more useful. In this release there are also quite a few optimisations to the sync process so in some cases it should be faster, as well as better support for WebDAV. Finally there are various small fixes and improvements, such as support for SVG vector graphics, improved math formula support, etc.
All these improvements are also found in the recently released macOS, Windows, Linux and Android versions.