Just found this in the Amplitube forum….

“One of the major improvements of #AmpliTube 4 iOS can’t be seen but can be heard! We ported the algorithms of the desktop version of AmpliTube in this new mobile version, refactoring EVERY single piece of gear, so you will have the best possible sounding amps, stomps, cabinets and more now always with you in your iPhone and iPad.
This is huge. ”

If they’ve cracked this, it is a huge step forward. Amplitube on iOS was pretty poor from a sound quality perspective so this could be a huge improvement