Great question! Since we are at feature parity for all applications (web and iOS), there's no significant difference between functionality on the two platforms.
The native iOS application will always have a performance advantage due to the way it's built, and we will provide support for Apple-specific features in the future ... but we cannot tell you about that quite yet! Stay tuned.
Our product team would love to hear your ideas, feedback, bug reports, and feature requests! Please visit our ideas board to submit those. => https://trello.com/b/JDz14ymX
This may change in the future, but for now, enjoy whichever app you prefer.