The thermal performance of fiberglass insulation is directly related to its ability to trap and maintain very small pockets of air. Blown-in fiberglass creates a seamless blanket in your attic. You might spend many hours kneeling in your attic to achieve this same result with fiberglass batts.
The thermal performance or resistance to heat flow (R-factor) is not the same when comparing fiberglass batts to blown-in fiberglass. Batts offer a slight advantage. You can usually obtain an R-factor of 3.1 to 4.2 or slightly higher per inch of material with batts. The R-factor of blown-in fiberglass is usually 2.3 to 2.8 per inch of material.
Once installed and expanded to the uniform, manufactured thickness, batts offer a known R-factor. Blown-in insulation thickness can vary in an attic space. This will lead to non-uniform R-values.
Before you make your final decision, do a cost analysis. You may be pleasantly surprised. I recently priced the cost to upgrade a 1,500 square foot attic from R-19 to the new thermal standard of R-49 in my climate zone. The total cost to have the fiberglass blown-in by professionals was $0.40 per square foot or $600. I then called the local retail outlet to price batt insulation. The cost of just the material was $0.45 per square foot! Clearly it made better sense for me to have the job done by professionals.