Larger API Capability
More Granular Control over Execution
Increased Performance
Native Device Storage
Apple's App-Store
Drawbacks
Objective-C Dependency
XCode Dependency
Objective-C/XCode Programmer Dependency
iPhone/iPad Builds Only
Testing Requires Builds
Apple's Censorship
Potential Blindness of Apple Fanboy Programmers
Update Management
Extremely Low IP Theft Risk
Sencha Touch
Benefits
Sufficient API Capability for Most Application Needs
Multi-Platform Capability (Desktop/Mobile - iPhone/iPad/Safari/Chrome/Android)
iPhone/iPad Add To Home Screen Deployment
Rapid Test Capabilities
Rapid Deployment via Web
Rapid Speed to Market
No Censorship
Programmer Base More Willing to Adopt
No Update Management for Clients
Drawbacks
Limited API Capability *
Limited Device Storage
Performance Limited by Browser Capabilities **
Requires a Wrapper App for Apple's App Store
Sencha/Javascript Dependency
Sencha/Web Programmer Dependency
High IP Theft Risk (Users can see UI/Webservice Code) ***
I'm sure there are more pro's and con's, but these are off the top of my head.
* Most business applications will not need what the Native API offers.
** Requires research and benchmarks.
*** Software Development Firms May Risk Exposure of UI Code to 3rd Parties.