The two options for running magic in ICRPG have been discussed at great length.
The simple roll-to-cast method is what almost everyone uses. As the system and audience grew, there was a wide desire for a more in depth OPTIONAL system…thus the OPTIONAL casting system here was born, and eventually cleaned up.
My fav mage I ever played in ICRPG used the optional system, using HP (old way) instead of SP (new way)… it was a fantastic experience because I could tailor my strategies to the moment. If good-old roll-to-cast fits best, just use that and don;t sweat the more complex system