I would have to agree with SD's comment about the boom vang. With regard to a preventer on both our booms at least, we are able to attach a preventer to the end of the boom and then run it forward to a snatch block then aft to the cockpit when needed. I guess it depends on the hardware and configuration at the back end of your boom.
I agree the jiffy or slab setups are more preferable. I can't speak to the in boom systems or in mast systems as I have never owned or sailed that equipment.
Let us know what you decide.