Yeah, it totally depends what you want to do; do you want to mostly build large or small props? Do you want to work mostly with thin and delicate materials, or with more hefty materials like in construction? It also depends what kinds of tools you already have; if you already have a jigsaw, than a scroll saw will give you more versatility. If you don't have any power saws, than a band saw will take care of a lot of your general cutting needs.
I personally never use a scroll saw (but then, I rarely make anything smaller than a fist); if I need to do anything precise and delicate, I'll attack it either by hand or maybe with a Dremel. I find a band saw extraordinarly useful for cutting all sorts of stuff, from thin plastic up to really thick wood. Also, if you ever want to cut thick styrofoam, a bench top band saw can usually cut pieces around 3-4" thick, while a scrollsaw may only let you do 2-3".