Well, you could narrow your choices by understanding the types of materials and processes you can use for 3d printing and then once you know each of their strengths and weaknesses you can choose the right type of printer for you and from there it is just a matter of how much do you want to spend vs. quality. So today there is FDM printing which is the plastic filaments. There is SLA which is light cured resins, and there is SLS printing which is sand that gets cured by lasers. I personally prefer the FDM because the filament is cheap and the prints with a thick layer height are nice and strong. The light cured resin stuff looks great but the resin is pricey, hard to store because you know it cures with light, and the resin prints are weak so resin does not make for good functional parts. And you have to do your own diligence on the Selective Laser Sintering(SLS) printing. I know it is out there but don't know too much about it yet.