I realize my response will likely not be of much use to you, since it is indeed a matter of opinion on my part. However, here goes. In my opinion there are only two reasons to print an image on canvas, which are as follows. Simply put, a canvas print should have the "look" of canvas, as well as the tactile properties of canvas, including the ability to actually feel the stretched material as it gives to the touch and then returns to its previous stretched tension. As a matter of fact, when I tell a customer that the print hanging on my wall is on canvas I also ask them to touch it, feel the give and take nature of the fabric, as well as the canvas texture itself. Indeed, feel and hear the effect of a gentle tap on the surface, almost bass drum in nature. To me that is the essence of, and the reason for printing on canvas. In other words, a canvas print should exhibit a sort of "organic" presence, which can be enjoyed by at least two of the senses, sight and feel. Now of course I am not, and would never suggest that one should encourage all viewers to exercise the second of those two senses(feel) with a canvas on exhibit in ones home, except in extraordinary circumstances.
For the reasons mentioned above I cannot seem to put any sort of value on a canvas that has been mounted on a solid substrate, although I do of course understand that in some cases it would be the customers wish to do so, and we all realize that the customer is always right. As far as printing on an ultra smooth canvas is concerned, why not simply print on a good quality fine art paper? Less work and no stretching involved. As for the easy "Peel and Stick" variety of canvas stretching I would offer a bit of advice. Indeed it is a very easy, fast and less expensive way of finishing the job. However, as with many applications, easy, fast and inexpensive is not always the best route. When I first researched this method I immediately had my doubts about its permanence. I simply could not believe that a properly stretched canvas could be maintained for any length of time by any sort of adhesive, except perhaps "Gorilla Glue". For many years I have been printing enlargements for a local Photo-Finisher, as a subcontracted addition to my own base of steady customers. The work for the Photo-finisher also consisted of canvas printing, which they would then stretch using the Peel & Stick method. In many cases, within the last few years a number of those canvases have been returned for re-stretching, since the adhesive had let go and the canvas had slacked to the point where it could no longer be displayed, something I had also warned them about previously. Now I do believe that if one were to leave enough extra canvas to wrap around the back edge of the bars it could of course be stapled, as in a traditionally stretched canvas. In this way I suppose the Peel & Stick method could perhaps find a place in the stretching procedure, except for the possibility of the a conflict between the two methods of adhering the canvas to the bars. If it started to slack with time, one would then need to undo both the staples and the adhesive in order to re-stretch. Not a preferred method I'm sure.
Again, this is strictly a point of view on my part, but I hope it might add some fuel for thought to the conversation.
Gary