iPhone apps are limited by the functionality that the iOS provides. They are also limited by the processing power of the device they run on. The iPad has way more ooomph than the original iPhone. Yet most apps have to run on all devices.
As for iOS: with the advent of OS3 almost all apps moved up to use the pasteboard.
It is the single most important secret weapon audio apps have to make sure mobile music creationists can compose on the go: it enables apps to pass on audio and receive audio.
Most audio apps are very specialized to do a certain task very well while only being marginally competent for other things. So in order to have good tools for all aspects of music creation, you will need apps that can talk to each other and pass audio on.
Apps at AppStoreHQ
Last year Sonoma Wireworks introduced audiocopy and paste. At the time, I just finished my pasteboard for audio files. While my system did have a few advantages, I still felt that audiocopy was the better solution overall and decided to scrap my work to support Sonoma and prevent a split of the community.
Audiocopy copies wav files to the pasteboard. It also encapsulated information about the audio, like what app it is coming from, bpm, length and number of channels. The latest incarnation of audiocopy has a history of 12 files available so you can in essence copy 12 files from one app to many. The support of the general pasteboard is just icing on the cake to re-unify the split of the audio-app community.
That’s what I call the audiocopy network. It is an important stepping stone to mobile music. You should not buy audio apps that do not support audiocopy as those apps will always be inferior to the audiocopy network.