I don't think it makes any difference in general.
Possible exception for WW1 postcard, which are sent from the front by a soldier.
I do have a few customers though, who buy postcards purely for the postmark, rather than the image on the card.
A lot of my customers like cards with stamps and cancel, I can tell when a buyer purchase 10 cards from me and all are cancelled -------- I prefer cards with cancel & stamp to document when card was actually mailed
Most picture postcards are rarely unique when still mint.
Postally used picture postcards, that are in a good condition or even better, can be considered the closest one gets to unique items telling a story of its own. That is also what I prefer to collect, but some postcards are really hard to come by in a postally used condition.