Well, injection allows you to fill multi-cavities in one fell swoop and is fairly mess free. With stick baits, top pour gives you the same results except you have to fill each cavity individually. You still have tp top off both methods in most cases. It is easy to top pour injection style stick bait molds, but not molds with thin appendages. With top pour molds, you can get away with a microwave and a pyrex cup. I started with top pour and graduated to injection, but there were not a lot of options then.