Some of the reasons our customers have chosen us in the past include:
Performance. Our charts use OpenGL ES for super slick initial rendering, panning and zooming. We also have very efficient handling of data points which means you can have lots of data on screen at once!
Gesture Support. Mobile users inevitably want to be able to interact directly with the UI and your data, which is why we've placed a lot of effort into full multi-touch support. This includes gestures for panning, zooming, highlighting and annotating a chart's data.
Support. ShinobiCare gives easy access to all our fixes and upgrades for a year. ShinobiCare Plus adds access to our Dev team (like myself!) who can help you with any queries you might have.
Documentation. Apple have set a very high standard with their UIKit documentation, so we know from experience that top quality docs can really speed up the development process. This is why we spend a lot of time ensuring our API docs are clear and concise and that our user guides provide more detailed explanations of exactly how our libraries work. You can take a look at our offerings here - http://www.shinobicontrols.com/shinobideveloper/documentation
Chart Types. We support a lot of different series and axes types, which means it's really easy to visualize your data in whatever configuration you want. A complete list can be found here - http://www.shinobicontrols.com/ios/shinobicharts/price-plans
Platform Support. All of the above reasons also apply to our Android version of ShinobiCharts. And no worries if you'd rather code in C# - we take the time to roll out Xamarin bindings for both our iOS and Android versions for every release we do.
Having said all that, we do think that it's really important for developers to choose a library that's right for them and their project. Feature lists and technical promises might go someway to helping you decide, but the best way to get a feel for any library is to give it a try! - http://www.shinobicontrols.com/ios/shinobicharts/price-plans/shinobicharts-premium/shinobicharts-free-trial-form
I hope that the above is useful info. Don't hesitate to get in touch if you have any further questions!