There are usually a few differences between the different platform versions as each is updated successively. You can compare them here:
http://www.irealb.com/features/
Obviously the iPad would give you a larger screen, be more responsive and currently gives you other options (like audio export, chords, scales and loops) if these are important for you.

Also you might be interested in multitasking with other iOS apps (especially if you are guitarist, bass etc.)
http://irealb.com/forums/showthread....g-using-Player

I am not trying to do the hard sell thing—just making sure you know what to think about in making your decision.