I thought about this as well before jumping in. What stuck out to me--and would not be visible on the shelf--was that Sub Press's were leather-bound, while CD's--in keeping with the majority of their limited editions--is clothbound. Ultimately, I decided that any differences between the two presses would not bother me too much. I would be bother much more by having a lettered edition of the third or fourth book and the rest being limited editions.
As far as Speaks The Nightbird, I'm hoping we'll get a new edition. I have heard some unfortunate things about the current limited edition. From Camelot Book's page:
Now, for those of you that are not aware, the production of this book was not good, the weight of the pages is causing the spine and endpapers to separate from the pages/board corners,