It seems to me that iOS is not focused on tracking user activity. Some apps are but no-one forces you to use them (or enable their tracking). I'd be much more concerned about vanilla Android installations. On the other hand, Android devices (e.g. I own a Nexus 7) are not locked down at all (sometimes in a bad way -- I suspect something equivalent to the Bad Old Days of Windows malware is in the Android near future).
Quite a few gcc/vim/shell-centric developers use iPads as terminals and they work very well for this (with or without a keyboard).
That said, I'm typing this response on a Macbook Pro.
By default, Android devices are locked down in 2 ways - you've not got root, and you can't install unsigned non-market apps (though trust of market apps is somewhat of a joke).
You can obviously gain root, and you can easily tick the box to allow unknown sources, but it seems likely that 99% of Android consumers are not going to do this without a decent reason.
Quite a few gcc/vim/shell-centric developers use iPads as terminals and they work very well for this (with or without a keyboard).
That said, I'm typing this response on a Macbook Pro.