anelab26:
It's really up to you: depends upon "tastes", funds, size, and weight considerations.
I've been using an iPad for my primary computer device since the iPad Retina (the 30 pin version, that only sold for about half a year).
I moved to an iPad Pro, 12.9" (2nd gen.), about a year ago.
I like the larger screen, but it is heavier.
For my wife, we, first, got a first gen. iPad Pro, 11", but that was stolen, before we had it long (and we've never seen it since).
More recently, we got her an iPad Air, 11". It's nice and light, for her. (I like it too, when I use it.)
With iCloud storage, I have had little issue with sufficient storage. (I turned on iCloud Storage for all Apps that had the option, early on.)
For note taking, you may want to use an iPad that's compatible with Apple Pencil (though there are other options, but with lesser capabilities, generally). (As of this writing, there are two generations of Apple Pencil, with fewer iPads compatible with the more recent, and more capable, Pencil.)
So many choices!