iOS does not have a tenth of the musical instruments, effects or sequencers that Windows VSTs have.

It's a turtles-all-the-way-down situation. I've toured with musicians before, and they are not jamming on iPads or plugging their DAC into an iPhone. They're running full-fat computers, real Omnisphere presets and the total Melodyne suite, not the pedestrian trial versions that the App Store sells.