I'm very much skewed to the published side. 99%. In my 20 years of collecting I personally commissioned one piece, and only because it was part of a charity event.
I might have acquired 2 finished unpublished pieces at some point. They didn't stay long in my collection As they did not have what I consider the attractive part of Collecting Original comic art.
I started collecting Original comic Art because I could see the published printed version of it, and the appeal of owning the original of it. Besides the cost effectiveness, I never understood collecting unpublished or commission pieces. I rather save the funds for a publish piece.
If cost was the factor, I would much rather go the route of prelims, as they would reflect and resemble the final version of the publish piece.