Which is better blow in insulation or lay down insulation?

I want to insulate my garage but I am not sure which works better blow in insulation or rolled insulation? My garage is 10 x22, their is no insulation in the rafters but my garage is drywalled.I want to insulate it but not sure to blow or roll it. I know what R value has to do with insulation but what is a good R value for my garage, I dont want to over do it. Also money wise would it be cheaper to buy rolled up insulation or blowing it. Is blow in insulation better or worse as the rolled up insulation? Thanks