If you just want to sketch ideas, garage band could be enough. I mean both a Mac and iPad are quite portable, but i do see if you just want to professionally develop music on the cheap, iPad it is, you will have a hard time with the screen size however if you want to anything with many instruments and tracks
Yea, granted. I don't have any issues carrying my m2 air about for writing but it's still a bit cumbersome vs. ipad and I'll be trying out the new version for sure. Just seems complimentary rather than binary.