As a professional fine-art printer myself, I have increasingly come to favour and recommend smooth-surface, matte cotton papers for their unobtrusiveness - Innova Smooth Cotton Natural White or Hahnemuhle Photo Rag Ultra Smooth. Definition is finer than with, say, vanilla Photo Rag, hand-feel is lovely, customer is happy. For the deepest blacks and widest gamut, you need to go for a top-quality baryta, such as Hahnemuhle Photo Rag Baryta or the Canson equivalent, as long as the pigment inks are coated or encapsulated to avoid bronzing - my machine lays a fine varnish down over the final print.
Watercolour papers and canvas don't print with quite the same fidelity, and ironically, are worse for printing watercolour or oil paintings, as the texture of the paper clashes with the texture of the picture.