iCalendar is different from Pocket Informant, in that iCalendar is just a bare bones calendar. Pocket Informant has some additional features, like audio notes, contacts, tasks, and notes. The contacts are synced from your iPhone, and the tasks can also be synced with an external to-do list. I like Pocket Informant because it synchs with my Toodledo list. Most of the time, I am using iCalendar and Toodledo separately, because they are more responsive by themselves. However, I sometimes use Pocket Informant because it presents a tasks and appointments view of my day. For what I have researched, Pocket Informant is the best for this. The sync for Pocket Informant is a little slow, but the last upgrade had improved this substantially.