In Blood Bowl Team Manager, are Freebooter Stars supposed to be more or less powerful than their regular counterparts?
It makes a big difference when you gain the star player.  Gaining the average freebooter in the first round is better than gaining the average non-freebooter (there are always specific exceptions of course) because you will get to use that player statistically more often due to the smaller deck size.  Conversely, gaining a freebooter in the fourth round is potentially useless, as you want any star players you gain to come into play in the last round; only the ones put on top of your deck are guaranteed to do this.  The tipping point is somewhere in between.

One other consideration is how much sprinting your base deck has.  Decks with more sprinting have less use for freebooters because they can filter their deck mid-game.  Consequently, it is better to have more powerful characters to get the most value out of the sprinting ability.