It would be convenient when changing the document size automatically recalculate the size (for non pixel units) <-> DPI as in Photoshop when "Resample" is disabled:
The dialog might look something like this:
A feature that still gives Illustrator a slight edge over AF is the vector 'filters' and 'effects' - things that change the appearance of the vector paths [ which can then be 'expanded' into curves if need be.]
For instance there is a simple 'roughen' effect [or filter] that can be applied to the vector shapes in illustrator
Another example is the powerful feature of the 'transform' effect. see image
I know I've suggested a similar feature, but all this talk of smoothing curves brought this up in my mind; in addition to a tool to smooth a curve, Affinity Designer should also have the opposite. I am of course referring to Midpoint Displacement, which would allow illustrators to make non-uniform curves more easily than having to draw each node individually.
Being able to smooth curves is indeed important, but as it is, it's really hard to produce a line that doesn't look uniform, and a roughening tool to add pseudorandom midpoint displacement would make illustrating much less time-consuming.