I am building an app for android 4.4+. Will adding crosswalk give any performance benefits for me? From what I understand crosswalk helps older devices by installing a newer webview into them, but if my devices already have 4.4 is there any point? Am I understanding the concept of crosswalk properly?
Cheers
Think of Crosswalk just as an alternative browser which is packaged with your app. It has it own benefits, but also some downsides. Its not about being newer or better.
Some pros:
You know what you get. How big your company might be, you can never test your app on all devices and versions. if you take crosswalk your app always behaves the same. It doesnt matter if its on a Huawei Ascend with Android 4.1 or on a Samsung S6. The layout, the behaviour in general are always the same (of course there are performance differences)
It performs better on older Android Versions, since until 4.4 the used webview is just not capable of competing with the newer versions or crosswalk for example. Additionally there are always differences how CSS and your markup is interpreted.
input type file everywhere \o/
Its in heavy development and cordova fully supports it by now, so you can expect it to get better and better especially for ionic.
Some Cons:
Its in heavy development. 
there are some bugs and issues but most of them are minor.
Your apps filesize will increase, approx. 15-20mb
Theres no Automated Testing tool (like Ranorex for example) which supports Crosswalk, so for these you end up building two versions of android (one without xwalk). Of course this is everything but optimal.