first I'm thinking of the cover price of that book. sure I would be getting 2 comics for probably about $5 but what if I not really interested in one of the title characters.
I may go with giving them 11 pages so the cost is similar to other comics.
of course since these are two characters that had lagging sales I'm not sure if they will do that well in a book together. Maybe two books splitting them up with characters that are a more popular.