[davidhbolton]

If performance is an issue then native tools such as Java, Swift or even C# are indeed the way to go. My own experience with C#/Xamarin on iPhone 6 was that it was very performant, in excess of what I anticipated. A specific example. I built a Uber type app using the Google iOS SDK.

It held all UK addresses (out of 29 million and 350,000 points of interest-ATMS, supermarkets, railway stations etc) within a 25 mile radius cached in RAM. Scrolling the map with your fingers, it used the lat/lng of the screen centre and was able to search the in-RAM addresses to return the street the map was over as a String. This matched what the map was displaying.

If you did a search of an address as it was typed character by character, within 1/10th of a second it could return the top 100 matching addresses, sorted by proximity. I challenge anyone to do that in JavaScript!