A whole lot more oomph. What Pony Express said. This is Hodgdon's description:
IMR 4227 is a medium burn speed, magnum pistol propellant. If a pistol says Magnum, IMR 4227 is the choice for true magnum velocities and performance. In rifles, this powder delivers excellent velocity and accuracy in such cartridges as the 22 Hornet and 221 Fireball.
For 38 spcl, the only data they show for a lead bullet is a 158gr LSWC, 8.0 to 9.0 gr for 887 to 983 fps. Loads with lighter bullets would probably be faster.