Yeah grinders are great because they cut the weed up into pieces that are relatively the same size. This allows for maximum airflow and exposure of THC. That's why its so much easier to rip a bowl of grinded weed versus a shitty bowl of finger broken.

Plus its faster, which leaves more time for smoking

PS - The only grinder you should ever buy is a SharpStone. Unbelievable, even does an ok job of grinding really sticky weed. It also has a THC catcher in the bottom, and after you grind about a quatch, you'll have enough for an entire bong rip of keif. See you on the moon my friend.