NoteSuite, a powerful note taking app on Mac & iOS.

Some reasons I use NoteSuite every day.
Syncs flawlessly with the Mac app, too.

Source site:
http://www.application-systems.co.uk/notesuiteipad/comparison.html

		NoteSuite for iPad		Evernote		Notability
Basic Features
Capture notes, documents, photos, and audio together						*
Clip articles, pages, and PDFs from web
Manage priorities with full-featured to-do manager
Draw on notes with digital ink
Annotate PDFs
Annotate Photos
Convert MS Office files to PDF for Annotation						*
Search MS Office files				$
Type in any font, style, or size
Create lists, outlines, and to-dos within notes				**		**
Email notes and documents to notebook
Organize notes by folders or tags
Find misplaced files without keyword searching
Accessibility
Sync between iPad and computer
Access everything offline				$
Keep notes permanently
100% availability -- no server downtime or account lockouts
Advanced Features
Place PowerPoint slides within notes
Automatically shrink handwriting to fit better on iPad screen
Drawings and handwriting stay connected to text while editing
Convert Apple iWork files to PDF				$
Expand and contract sublists to switch between details and big picture
Rearrange items in lists by dragging
Record audio synced with text in notes
PDF Annotation
Draw freehand and place shapes on PDFs
Highlight, underline, and strike-through text
Create comment balloons
Create bookmarks
View Table of Contents
See excerpts of all Highlights
Flatten annotations to be viewed by others
To-do Manager
Track due dates and set reminders				***
5 quick ways to capture to-dos within notes or to-do lists
Set start dates to give yourself enough time to do things
Today list automatically shows everything that needs attention today
Manage projects and sub-lists
Assign to-dos to other people and email them details
Create repeating to-dos
Add to-dos to your calendar
Organize to-dos by tag				****
Quickly create to-dos while writing notes or reading documents
Write to-dos wtihin note text and gather automatically into master list
Automatically calculate due dates based on natural sentences
Email to-dos directly to to-do list and attach documents
Instantly find all notes and documents related to a to-do
GTD compliant