why can't it be both-just because you said....
I have built my set (still need about 10 fronts) making sure I get at least 10 examples of each back ad. I have several examples of the fronts that I like the most and the same goes for the backs.
Also I have moved to other vintage sets because there are too many collectors that focus on 206s. I will always pick up 206s but there is so much more out there.