User blog comment:FairyRaven/One-time-only Spells/@comment-904888-20120709005643/@comment-904888-20120709125129

Add to the fact that so far, everything points to Glitter being much faster to cast than Law, and nowhere near as defenceless (at least from the looks of it, Jose was gloating at Makarov when he was casting it, and only tried to attack Makarov when the spell's power have been fully prepared. Laxus paralyzed Natsu and Gajeel prior to casting it so they cou;dn't do anything to him. Finally against Grimoire Heart... I don't know, it is faster to cast law than chase every one of the cronies?). Glitter seem to have a painful paralyzing effect while it is being cast, thus preventing the target from retaliating easily.