This depends on the installation.  On many street-driven vehicles, where the master cylinders and other items protrude into the engine compartment, it’s probably necessary to use head bolts so that the cylinder heads can be removed with the engine in the car.  For most applications, however, studs are recommended.  Using studs will make it much easier to assemble an engine with the cylinder head and gasket assured of proper alignment.  Studs also provide more accurate and consistent torque loading.

Most applications from ARP are head studs and very limited head bolt applications listed.  Titan Motorsports recomends using Head Studs over bolts as they provider better and more accurate torque specs.