Just a personal preference, but I prefer batting if the area is accessible. Batting has a built-in vapor barrier. It is able to be moved around to facilitate repairs in the future. It stays where you put it, and is easily adjusted if the installer inadvertently blocks roof vents or soffit vents or if you do a remodel/renovation. Batts do not release as much fiber as blown, but avoiding glass fiber insulation is still a good idea. Costs more, because of time needed to cut to fit as compared to blown insulation.
Blown in cellulose is a good insulator. It contains ammonium sulfate and boric acid as preservative, insecticide and fire retardant. Its a mess if you ever need to do a repair from below and it isn't much to look at. You need a vapor barrier or the insulation can be damaged and compacted. This stuff takes forever to dry if it becomes wet, that is why it is also used in hydromulch (dyed green, fertilizer and seeds added). No known human health hazards. Quality can vary widely depending on manufacturer and source of paper fiber. Your vendor should tell you brand of product. Look up their web site. If material is not from large reputable company, look elsewhere.
Blown in glass fiber is an effective insulator and is impervious to insects and fire. Glass fiber must be isolated from the living space and ventilation for health reasons. Does not absorb moisture, but should have a vapor barrier. When blown-in, you won't see rafters (where to step). This can make going in the attic an adventure.