You can dissect a Starter, a lot better then a Reliever. Number of Pitches, times through the line-up, you have some kind of gaging on a Starter then a Reliever.
Very few stats on any Starter after 7, your in uncharted territory. Feel for the game, good communication with Catcher, and Pitching Coach, the old fashion way.
Easier to use Computer. Maybe good, maybe bad.
Reliever needs to do one thing mainly, throw strikes. And try to make them unhittable.