I use Titanium, which has a map view built upon the native specific maps for iOS and Android.
What would be the difference between using a native map and opening a webView with google maps loaded inside.
What would be some performance hindering differences between the native maps and one loaded from the web in a webview?
In our experience MapKit (i.e. Native) is much, much, faster and smoother that using a UIWebView containing Google Maps. It’s slower to start up as all the map rendering code has to be downloaded from google’s servers, and it’s quite a lot slower to render as it’s in a browser. Theoretically apps running in a browser can be just as fast and smooth as Native, but in actual reality this rarely happens.
Even on a iPhone 4S the difference between native and browser is noticeable. Android is even slower as, except perhaps for the very latest devices, the web browser doesn’t use hardware acceleration.
If you have the choice, always go native.