For me, it's not the feature set of any portable solution but the real-estate.
I grew up on Pro24 on an Atari, with a 12" screen. This was already a vast improvement on previous hardware sequencers, with nothing more than a tiny LCD display to work on.
It's the equivalent of trying to decorate the hallway through the letterbox.
That references an old joke I'm not sure is appropriate for in here ;-)
Since the 90's I've had two screens - as large as could be obtained at the time, & currently work on two 1440p 27" displays.
That means I've room for my main arrange page on one & my mixer on the other, with enough room left to have half a dozen plugins open at the same time, without everything being hidden behind everything else.
So, sure, you can work on an iPad Pro... but only if you're willing to give up all that screen space.