Allyn Gibson wrote:
The advantage to mini-series is that they can mimic the same event-driven, epic storytelling that the novel lines deliver today. The advantage to an ongoing series with single issue storytelling and longer story arcs is that it mimics the episodic nature of the television series that has, to some extent, been lost.
Although IDW has now done two TOS mini-series set in "Year Four", with some potential overlaps (eg. developing Arex; perhaps setting up Chekov to move into security?), and a promise of more to come. The graphic novel omnibus reprints have numbered spines which should climb if/when more is done.