I am going to insulate my attic but I am deciding between spray foam or blown in insulation. Does anyone have any advice or things that I need to think about for my decision?

We've decided to use blown-in cellulose over our fiberglass batting insulation in the attic. Before they blow the cellulose, they are going to seal all ceiling penetrations and also channels such as the space around chimney stacks. It's also important, if you have vents in your eaves, to have soffit ventilation installed so the insulation doesn't block the soffit vents or become damaged/moved by the wind flow. Our choices were additional fiberglass or the cellulose - spray foam seems very "permanent."