Assuming both categories got the same attributes,
there is no difference in query performance (According to Multiple Table Select vs. JOIN (performance) )
In that case the solution with one table uses slightly more storage than the two table solution as you need a further column for differentiation (e.g. type).
EDIT
As your structure is different, you should use the two-table-solution as you get NULL
fields if you use the one-table-solution.
A bad example for the table Publications
:

In the given example you do not need an additional attribute to differentiate the two types because you could determine the type by Pages
or Director
.
You should avoid NULL
values, especially when they are not meant to be filled with data in the future.