A reader of my recent MSDN Magazine article asked what I thought about performance in Cordova apps, and here's what I wrote in response.
Performance really depends on the underlying hardware, the individual platform, and the version of the platform, because it’s highly dependent upon the quality of the app host and hardware that’s running the code.
On Android, iOS, and Windows Phone 8, Cordova apps run JS inside a Webview, and thus are very much subject to Webview performance. From what I've heard–and I haven't done tests to this effect myself–performance can vary widely between platforms and platform versions. More recent versions of the platforms, e.g. iOS 7/8 and Android 4.2 or so, have apparently improved Webview performance quite a bit over previous versions.
In short, if you’re targeting the latest platforms, performance is decent and getting better. If you're targeting these systems, then, Cordova performance should be suitable for many types of apps, though probably not for intensive apps.
It's important to note that "performance" is not really a matter of throughput: it's a matter of user experience. I like to say that performance is, ultimately, a UI issue, because even if you don't have the fastest execution engine in the world by some benchmark measure, you can still deliver a great experience. I think of all the video games I played as a kid on hardware that was far inferior to what's probably inside my washing machine today. And yet the developers delivered fabulous experiences.
I made a diagram that’s on http://www.visualstudio.com/explore/modern-mobile-apps-vs that tries to illustrate where Cordova falls relative to Xamarin, native, and mobile web. The vertical axis is “mobile app user experience” which includes perf as well as the ability to provide a full-on native experience like I just mentioned.
The diagram is one way to look at the relative strengths of different cross-platform approaches. In the end, you of course have to decide what perf measures are important for your customers, do some tests, and see if Cordova will work for your project. And of course, pester the platform providers to improve Webview perf too!