Currently on my ipad, I use a recording program called Auria. It is a DAW,not just a recording app. As with most creation or recording programs, it consumes memory. Right now with just a few songs (in which all tracks were created in Real Band and moved to Auria to add my vocals) it consumes over 6gb. I move songs to Dropbox for storage or to my PC. I currently have 64gb of memory in total. The problem is not often the programs, but the songs you create eat a ton. One song with five tracks in a recording program can eat up 250mb of space.

I have not yet tried to use the ipad for BIAB.

Rockstar is right about how much you can afford and also correct in making music with only 16gb. There are tons of creation options available. The I/O platform offers more creative possibilities than any other (through the millions of music creation apps) and often at a price you can afford. I guess that's probably the strongest argument for an ipad.

I often go through the Auria forum to learn more about their program and everyone says, get all the memory you can afford. It's not the programs, but what you create using them that eats up the memory. You can do like I do and move things to the cloud or PC or buy up memory in the beginning. If you are very creative, have lots of time and you are a hoarder who wants to keep all you stuff on the ipad like me, you will run low on memory no matter which level of ipad you chose.

If the programs/apps you use are specific to ipad, you may not be able to move them somewhere for storage.

Just my thoughts and experiences. Great tool though. Music creation at its easiest level.