Every OS platform has it strengths and weaknesses, and users of each of these different OS platforms tend to have different expectations about subtile features in the UI behavior and the look and feel of apps running under their chosen OS & hardware.
If you already have the knowledge and experience to build and customize your apps for iOS and Android (and/or webOS, et.al.), using the tools and SDKs they were designed for, then you will likely be able to create a user experience better tuned to the typical users expectations, and with a reduced likelihood of needlessly increasing memory usage or decreasing battery life by adding layers of CPU consuming library code.
Alternate development platforms seem to me to be for those developers who find time-to-market and cross-platform consistency of greater value to them than spending the time to learn and to use the skills needed to optimize their apps for the capabilities for each unique OS and its corresponding UI experience.