Web development VS application development
I would say web application development is more difficult than is native mobile application counterpart for the following reasons.
With those languages in hand the web developer will have to know lot of about the different behaviors across the many popular browsers like Firefox, IE, Chrome, and Safari including versions at least five years old.
The web developer will have to be able to write highly scalable code that handles many concurrently users. Performance bottlenecks can effect the responsiveness of the website because all of the clients are sharing the same infrastructure. For mobile applications much of the code runs on the phone and does not affect the performance of other users.